The term “selectable” refers to any object that rows can be selected from;
in SQLAlchemy, these objects descend from FromClause
and their
distinguishing feature is their FromClause.c
attribute, which is
a namespace of all the columns contained within the FROM clause (these
elements are themselves ColumnElement
subclasses).
Top level “FROM clause” and “SELECT” constructors.
Object Name | Description |
---|---|
except_(*selects, **kwargs) |
Return an |
except_all(*selects, **kwargs) |
Return an |
exists(*args, **kwargs) |
Construct a new |
intersect(*selects, **kwargs) |
Return an |
intersect_all(*selects, **kwargs) |
Return an |
select(*args, **kw) |
Create a |
table(name, *columns, **kw) |
Produce a new |
union(*selects, **kwargs) |
Return a |
union_all(*selects, **kwargs) |
Return a |
values(*columns, **kw) |
Construct a |
Return an EXCEPT
of multiple selectables.
The returned object is an instance of
CompoundSelect
.
Return an EXCEPT ALL
of multiple selectables.
The returned object is an instance of
CompoundSelect
.
Construct a new Exists
construct.
The exists()
can be invoked by itself to produce an
Exists
construct, which will accept simple WHERE
criteria:
exists_criteria = exists().where(table1.c.col1 == table2.c.col2)
However, for greater flexibility in constructing the SELECT, an
existing Select
construct may be converted to an
Exists
, most conveniently by making use of the
SelectBase.exists()
method:
exists_criteria = (
select(table2.c.col2).
where(table1.c.col1 == table2.c.col2).
exists()
)
The EXISTS criteria is then used inside of an enclosing SELECT:
stmt = select(table1.c.col1).where(exists_criteria)
The above statement will then be of the form:
SELECT col1 FROM table1 WHERE EXISTS
(SELECT table2.col2 FROM table2 WHERE table2.col2 = table1.col1)
See also
EXISTS subqueries - in the 2.0 style tutorial.
Return an INTERSECT
of multiple selectables.
The returned object is an instance of
CompoundSelect
.
Return an INTERSECT ALL
of multiple selectables.
The returned object is an instance of
CompoundSelect
.
Create a Select
using either the 1.x or 2.0 constructor
style.
For the legacy calling style, see Select.create_legacy_select()
.
If the first argument passed is a Python sequence or if keyword
arguments are present, this style is used.
New in version 2.0: - the select()
construct is
the same construct as the one returned by
select()
, except that the function only
accepts the “columns clause” entities up front; the rest of the
state of the SELECT should be built up using generative methods.
Similar functionality is also available via the
FromClause.select()
method on any
FromClause
.
*entities¶ –
Entities to SELECT from. For Core usage, this is typically a series
of ColumnElement
and / or
FromClause
objects which will form the columns clause of the resulting
statement. For those objects that are instances of
FromClause
(typically Table
or Alias
objects), the FromClause.c
collection is extracted
to form a collection of ColumnElement
objects.
This parameter will also accept TextClause
constructs as given, as well as ORM-mapped classes.
Produce a new TableClause
.
The object returned is an instance of
TableClause
, which
represents the “syntactical” portion of the schema-level
Table
object.
It may be used to construct lightweight table constructs.
Changed in version 1.0.0: table()
can now
be imported from the plain sqlalchemy
namespace like any
other SQL element.
Return a UNION
of multiple selectables.
The returned object is an instance of
CompoundSelect
.
A similar union()
method is available on all
FromClause
subclasses.
Return a UNION ALL
of multiple selectables.
The returned object is an instance of
CompoundSelect
.
A similar union_all()
method is available on all
FromClause
subclasses.
Construct a Values
construct.
The column expressions and the actual data for
Values
are given in two separate steps. The
constructor receives the column expressions typically as
column()
constructs,
and the data is then passed via the
Values.data()
method as a list,
which can be called multiple
times to add more data, e.g.:
from sqlalchemy import column
from sqlalchemy import values
value_expr = values(
column('id', Integer),
column('name', String),
name="my_values"
).data(
[(1, 'name1'), (2, 'name2'), (3, 'name3')]
)
*columns¶ – column expressions, typically composed using
column()
objects.
name¶ – the name for this VALUES construct. If omitted, the VALUES construct will be unnamed in a SQL expression. Different backends may have different requirements here.
literal_binds¶ – Defaults to False. Whether or not to render the data values inline in the SQL output, rather than using bound parameters.
Functions listed here are more commonly available as methods from
FromClause
and Selectable
elements, for example,
the alias()
function is usually invoked via the
FromClause.alias()
method.
Object Name | Description |
---|---|
alias(selectable[, name, flat]) |
Return an |
cte(selectable[, name, recursive]) |
Return a new |
join(left, right[, onclause, isouter, ...]) |
Produce a |
lateral(selectable[, name]) |
Return a |
outerjoin(left, right[, onclause, full]) |
Return an |
tablesample(selectable, sampling[, name, seed]) |
Return a |
Return an Alias
object.
An Alias
represents any
FromClause
with an alternate name assigned within SQL, typically using the AS
clause when generated, e.g. SELECT * FROM table AS aliasname
.
Similar functionality is available via the
FromClause.alias()
method available on all FromClause
subclasses.
In terms of
a SELECT object as generated from the select()
function, the SelectBase.alias()
method returns an
Alias
or similar object which represents a named,
parenthesized subquery.
When an Alias
is created from a
Table
object,
this has the effect of the table being rendered
as tablename AS aliasname
in a SELECT statement.
For select()
objects, the effect is that of
creating a named subquery, i.e. (select ...) AS aliasname
.
The name
parameter is optional, and provides the name
to use in the rendered SQL. If blank, an “anonymous” name
will be deterministically generated at compile time.
Deterministic means the name is guaranteed to be unique against
other constructs used in the same statement, and will also be the
same name for each successive compilation of the same statement
object.
selectable¶ – any FromClause
subclass,
such as a table, select statement, etc.
name¶ – string name to be assigned as the alias.
If None
, a name will be deterministically generated
at compile time.
flat¶ – Will be passed through to if the given selectable
is an instance of Join
- see
Join.alias()
for details.
Return a new CTE
,
or Common Table Expression instance.
Please see HasCTE.cte()
for detail on CTE usage.
Produce a Join
object, given two
FromClause
expressions.
E.g.:
j = join(user_table, address_table,
user_table.c.id == address_table.c.user_id)
stmt = select(user_table).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
Similar functionality is available given any
FromClause
object (e.g. such as a
Table
) using
the FromClause.join()
method.
left¶ – The left side of the join.
right¶ – the right side of the join; this is any
FromClause
object such as a
Table
object, and
may also be a selectable-compatible object such as an ORM-mapped
class.
onclause¶ – a SQL expression representing the ON clause of the
join. If left at None
, FromClause.join()
will attempt to
join the two tables based on a foreign key relationship.
isouter¶ – if True, render a LEFT OUTER JOIN, instead of JOIN.
full¶ –
if True, render a FULL OUTER JOIN, instead of JOIN.
New in version 1.1.
See also
FromClause.join()
- method form,
based on a given left side.
Join
- the type of object produced.
Return a Lateral
object.
Lateral
is an Alias
subclass that represents
a subquery with the LATERAL keyword applied to it.
The special behavior of a LATERAL subquery is that it appears in the FROM clause of an enclosing SELECT, but may correlate to other FROM clauses of that SELECT. It is a special case of subquery only supported by a small number of backends, currently more recent PostgreSQL versions.
New in version 1.1.
See also
LATERAL correlation - overview of usage.
Return an OUTER JOIN
clause element.
The returned object is an instance of Join
.
Similar functionality is also available via the
FromClause.outerjoin()
method on any
FromClause
.
To chain joins together, use the FromClause.join()
or
FromClause.outerjoin()
methods on the resulting
Join
object.
Return a TableSample
object.
TableSample
is an Alias
subclass that represents
a table with the TABLESAMPLE clause applied to it.
tablesample()
is also available from the FromClause
class via the
FromClause.tablesample()
method.
The TABLESAMPLE clause allows selecting a randomly selected approximate percentage of rows from a table. It supports multiple sampling methods, most commonly BERNOULLI and SYSTEM.
e.g.:
from sqlalchemy import func
selectable = people.tablesample(
func.bernoulli(1),
name='alias',
seed=func.random())
stmt = select(selectable.c.people_id)
Assuming people
with a column people_id
, the above
statement would render as:
SELECT alias.people_id FROM
people AS alias TABLESAMPLE bernoulli(:bernoulli_1)
REPEATABLE (random())
New in version 1.1.
The classes here are generated using the constructors listed at Selectable Foundational Constructors and Selectable Modifier Constructors.
Object Name | Description |
---|---|
Represents an table or selectable alias (AS). |
|
Base class of aliases against tables, subqueries, and other selectables. |
|
Forms the basis of |
|
Represent a Common Table Expression. |
|
Mark a |
|
Represent an |
|
Represent an element that can be used within the |
|
Base class for SELECT statements where additional elements can be added. |
|
Mixin that declares a class to include CTE support. |
|
Represent a |
|
Represent a LATERAL subquery. |
|
The base-most class for Core constructs that have some concept of columns that can represent rows. |
|
Represent a scalar subquery. |
|
Represents a |
|
Mark a class as being selectable. |
|
Base class for SELECT statements. |
|
Represent a subquery of a SELECT. |
|
Represents a minimal “table” construct. |
|
Represent a TABLESAMPLE clause. |
|
An alias against a “table valued” SQL function. |
|
Wrap a |
|
Represent a |
Represents an table or selectable alias (AS).
Represents an alias, as typically applied to any table or
sub-select within a SQL statement using the AS
keyword (or
without the keyword on certain databases such as Oracle).
This object is constructed from the alias()
module
level function as well as the FromClause.alias()
method available
on all FromClause
subclasses.
See also
Class signature
class sqlalchemy.sql.expression.Alias
(sqlalchemy.sql.roles.DMLTableRole
, sqlalchemy.sql.expression.AliasedReturnsRows
)
Base class of aliases against tables, subqueries, and other selectables.
Class signature
class sqlalchemy.sql.expression.AliasedReturnsRows
(sqlalchemy.sql.expression.NoInit
, sqlalchemy.sql.expression.FromClause
)
sqlalchemy.sql.expression.AliasedReturnsRows.
description¶sqlalchemy.sql.expression.AliasedReturnsRows.
is_derived_from(fromclause)¶Return True
if this FromClause
is
‘derived’ from the given FromClause
.
An example would be an Alias of a Table is derived from that Table.
sqlalchemy.sql.expression.AliasedReturnsRows.
original¶Legacy for dialects that are referring to Alias.original.
Forms the basis of UNION
, UNION ALL
, and other
SELECT-based set operations.
Class signature
class sqlalchemy.sql.expression.CompoundSelect
(sqlalchemy.sql.expression.HasCompileState
, sqlalchemy.sql.expression.GenerativeSelect
)
sqlalchemy.sql.expression.CompoundSelect.
bind¶Returns the Engine
or Connection
to which this Executable
is bound, or None if none found.
Deprecated since version 1.4: The Executable.bind
attribute is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Bound metadata is being removed as of SQLAlchemy 2.0. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.CompoundSelect.
selected_columns¶A ColumnCollection
representing the columns that
this SELECT statement or similar construct returns in its result set,
not including TextClause
constructs.
For a CompoundSelect
, the
CompoundSelect.selected_columns
attribute returns the selected
columns of the first SELECT statement contained within the series of
statements within the set operation.
See also
New in version 1.4.
sqlalchemy.sql.expression.CompoundSelect.
self_group(against: Optional[Any] = None) → FromClause¶Apply a ‘grouping’ to this ClauseElement
.
This method is overridden by subclasses to return a “grouping”
construct, i.e. parenthesis. In particular it’s used by “binary”
expressions to provide a grouping around themselves when placed into a
larger expression, as well as by select()
constructs when placed into the FROM clause of another
select()
. (Note that subqueries should be
normally created using the Select.alias()
method,
as many
platforms require nested SELECT statements to be named).
As expressions are composed together, the application of
self_group()
is automatic - end-user code should never
need to use this method directly. Note that SQLAlchemy’s
clause constructs take operator precedence into account -
so parenthesis might not be needed, for example, in
an expression like x OR (y AND z)
- AND takes precedence
over OR.
The base self_group()
method of
ClauseElement
just returns self.
Represent a Common Table Expression.
The CTE
object is obtained using the
SelectBase.cte()
method from any SELECT statement. A less often
available syntax also allows use of the HasCTE.cte()
method
present on DML constructs such as Insert
,
Update
and
Delete
. See the HasCTE.cte()
method for
usage details on CTEs.
Class signature
class sqlalchemy.sql.expression.CTE
(sqlalchemy.sql.expression.Generative
, sqlalchemy.sql.expression.HasPrefixes
, sqlalchemy.sql.expression.HasSuffixes
, sqlalchemy.sql.expression.AliasedReturnsRows
)
sqlalchemy.sql.expression.CTE.
alias(name=None, flat=False)¶This method is a CTE-specific specialization of the
FromClause.alias()
method.
Mark a ClauseElement
as supporting execution.
Executable
is a superclass for all “statement” types
of objects, including select()
, delete()
, update()
,
insert()
, text()
.
Class signature
class sqlalchemy.sql.expression.Executable
(sqlalchemy.sql.roles.StatementRole
, sqlalchemy.sql.expression.Generative
)
sqlalchemy.sql.expression.Executable.
bind¶Returns the Engine
or Connection
to
which this Executable
is bound, or None if none found.
Deprecated since version 1.4: The Executable.bind
attribute is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Bound metadata is being removed as of SQLAlchemy 2.0. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
This is a traversal which checks locally, then checks among the “from” clauses of associated objects until a bound engine or connection is found.
sqlalchemy.sql.expression.Executable.
execute(*multiparams, **params)¶Compile and execute this Executable
.
Deprecated since version 1.4: The Executable.execute()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. All statement execution in SQLAlchemy 2.0 is performed by the Connection.execute()
method of Connection
, or in the ORM by the Session.execute()
method of Session
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.Executable.
execution_options(**kw)¶Set non-SQL options for the statement which take effect during execution.
Execution options can be set on a per-statement or
per Connection
basis. Additionally, the
Engine
and ORM Query
objects provide
access to execution options which they in turn configure upon
connections.
The execution_options()
method is generative. A new
instance of this statement is returned that contains the options:
statement = select(table.c.x, table.c.y)
statement = statement.execution_options(autocommit=True)
Note that only a subset of possible execution options can be applied
to a statement - these include “autocommit” and “stream_results”,
but not “isolation_level” or “compiled_cache”.
See Connection.execution_options()
for a full list of
possible options.
sqlalchemy.sql.expression.Executable.
get_execution_options()¶Get the non-SQL options which will take effect during execution.
New in version 1.3.
See also
sqlalchemy.sql.expression.Executable.
options(*options)¶Apply options to this statement.
In the general sense, options are any kind of Python object that can be interpreted by the SQL compiler for the statement. These options can be consumed by specific dialects or specific kinds of compilers.
The most commonly known kind of option are the ORM level options that apply “eager load” and other loading behaviors to an ORM query. However, options can theoretically be used for many other purposes.
For background on specific kinds of options for specific kinds of statements, refer to the documentation for those option objects.
Changed in version 1.4: - added Generative.options()
to
Core statement objects towards the goal of allowing unified
Core / ORM querying capabilities.
See also
Deferred Column Loader Query Options - refers to options specific to the usage of ORM queries
Relationship Loading with Loader Options - refers to options specific to the usage of ORM queries
sqlalchemy.sql.expression.Executable.
scalar(*multiparams, **params)¶Compile and execute this Executable
, returning the
result’s scalar representation.
Deprecated since version 1.4: The Executable.scalar()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Scalar execution in SQLAlchemy 2.0 is performed by the Connection.scalar()
method of Connection
, or in the ORM by the Session.scalar()
method of Session
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
Represent an EXISTS
clause.
See exists()
for a description of usage.
Class signature
class sqlalchemy.sql.expression.Exists
(sqlalchemy.sql.expression.UnaryExpression
)
sqlalchemy.sql.expression.Exists.
__init__(*args, **kwargs)¶Construct a new Exists
object.
This constructor is mirrored as a public API function; see sqlalchemy.sql.expression.exists()
for a full usage and argument description.
sqlalchemy.sql.expression.Exists.
correlate(*fromclause)¶Apply correlation to the subquery noted by this Exists
.
See also
sqlalchemy.sql.expression.Exists.
correlate_except(*fromclause)¶Apply correlation to the subquery noted by this Exists
.
See also
sqlalchemy.sql.expression.Exists.
select(whereclause=None, **kwargs)¶Return a SELECT of this Exists
.
e.g.:
stmt = exists(some_table.c.id).where(some_table.c.id == 5).select()
This will produce a statement resembling:
SELECT EXISTS (SELECT id FROM some_table WHERE some_table = :param) AS anon_1
whereclause¶ –
a WHERE clause, equivalent to calling the
Select.where()
method.
Deprecated since version 1.4: The Exists.select().whereclause
parameter is deprecated and will be removed in version 2.0. Please make use of the Select.where()
method to add WHERE criteria to the SELECT statement.
**kwargs¶ –
additional keyword arguments are passed to the
legacy constructor for Select
described at
Select.create_legacy_select()
.
Deprecated since version 1.4: The Exists.select()
method will no longer accept keyword arguments in version 2.0. Please use generative methods from the Select
construct in order to apply additional modifications.
See also
select()
- general purpose
method which allows for arbitrary column lists.
sqlalchemy.sql.expression.Exists.
select_from(*froms)¶Return a new Exists
construct,
applying the given
expression to the Select.select_from()
method of the select
statement contained.
Note
it is typically preferable to build a Select
statement first, including the desired WHERE clause, then use the
SelectBase.exists()
method to produce an
Exists
object at once.
sqlalchemy.sql.expression.Exists.
where(clause)¶Return a new exists()
construct with the
given expression added to
its WHERE clause, joined to the existing clause via AND, if any.
Note
it is typically preferable to build a Select
statement first, including the desired WHERE clause, then use the
SelectBase.exists()
method to produce an
Exists
object at once.
Represent an element that can be used within the FROM
clause of a SELECT
statement.
The most common forms of FromClause
are the
Table
and the select()
constructs. Key
features common to all FromClause
objects include:
a c
collection, which provides per-name access to a collection
of ColumnElement
objects.
a primary_key
attribute, which is a collection of all those
ColumnElement
objects that indicate the primary_key
flag.
Methods to generate various derivations of a “from” clause, including
FromClause.alias()
,
FromClause.join()
,
FromClause.select()
.
Class signature
class sqlalchemy.sql.expression.FromClause
(sqlalchemy.sql.roles.AnonymizedFromClauseRole
, sqlalchemy.sql.expression.Selectable
)
sqlalchemy.sql.expression.FromClause.
alias(name=None, flat=False)¶Return an alias of this FromClause
.
E.g.:
a2 = some_table.alias('a2')
The above code creates an Alias
object which can be used
as a FROM clause in any SELECT statement.
sqlalchemy.sql.expression.FromClause.
c¶A named-based collection of ColumnElement
objects maintained by this FromClause
.
The FromClause.c
attribute is an alias for the
FromClause.columns
atttribute.
sqlalchemy.sql.expression.FromClause.
columns¶A named-based collection of ColumnElement
objects maintained by this FromClause
.
The columns
, or c
collection, is the gateway
to the construction of SQL expressions using table-bound or
other selectable-bound columns:
select(mytable).where(mytable.c.somecolumn == 5)
a ColumnCollection
object.
sqlalchemy.sql.expression.FromClause.
description¶A brief description of this FromClause
.
Used primarily for error message formatting.
sqlalchemy.sql.expression.FromClause.
entity_namespace¶Return a namespace used for name-based access in SQL expressions.
This is the namespace that is used to resolve “filter_by()” type expressions, such as:
stmt.filter_by(address='some address')
It defaults to the .c
collection, however internally it can
be overridden using the “entity_namespace” annotation to deliver
alternative results.
sqlalchemy.sql.expression.FromClause.
exported_columns¶A ColumnCollection
that represents the “exported”
columns of this Selectable
.
The “exported” columns for a FromClause
object are synonymous
with the FromClause.columns
collection.
New in version 1.4.
sqlalchemy.sql.expression.FromClause.
foreign_keys¶Return the collection of ForeignKey
marker objects
which this FromClause references.
Each ForeignKey
is a member of a
Table
-wide
ForeignKeyConstraint
.
See also
sqlalchemy.sql.expression.FromClause.
is_derived_from(fromclause)¶Return True
if this FromClause
is
‘derived’ from the given FromClause
.
An example would be an Alias of a Table is derived from that Table.
sqlalchemy.sql.expression.FromClause.
join(right, onclause=None, isouter=False, full=False)¶Return a Join
from this
FromClause
to another FromClause
.
E.g.:
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select(user_table).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
right¶ – the right side of the join; this is any
FromClause
object such as a
Table
object, and
may also be a selectable-compatible object such as an ORM-mapped
class.
onclause¶ – a SQL expression representing the ON clause of the
join. If left at None
, FromClause.join()
will attempt to
join the two tables based on a foreign key relationship.
isouter¶ – if True, render a LEFT OUTER JOIN, instead of JOIN.
full¶ –
if True, render a FULL OUTER JOIN, instead of LEFT OUTER
JOIN. Implies FromClause.join.isouter
.
New in version 1.1.
sqlalchemy.sql.expression.FromClause.
outerjoin(right, onclause=None, full=False)¶Return a Join
from this
FromClause
to another FromClause
, with the “isouter” flag set to
True.
E.g.:
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to:
j = user_table.join(
address_table,
user_table.c.id == address_table.c.user_id,
isouter=True)
right¶ – the right side of the join; this is any
FromClause
object such as a
Table
object, and
may also be a selectable-compatible object such as an ORM-mapped
class.
onclause¶ – a SQL expression representing the ON clause of the
join. If left at None
, FromClause.join()
will attempt to
join the two tables based on a foreign key relationship.
full¶ –
if True, render a FULL OUTER JOIN, instead of LEFT OUTER JOIN.
New in version 1.1.
sqlalchemy.sql.expression.FromClause.
primary_key¶Return the iterable collection of Column
objects
which comprise the primary key of this _selectable.FromClause
.
For a Table
object, this collection is represented
by the PrimaryKeyConstraint
which itself is an
iterable collection of Column
objects.
sqlalchemy.sql.expression.FromClause.
schema = None¶Define the ‘schema’ attribute for this FromClause
.
This is typically None
for most objects except that of
Table
, where it is taken as the value of the
Table.schema
argument.
sqlalchemy.sql.expression.FromClause.
select(whereclause=None, **kwargs)¶Return a SELECT of this FromClause
.
e.g.:
stmt = some_table.select().where(some_table.c.id == 5)
whereclause¶ –
a WHERE clause, equivalent to calling the
Select.where()
method.
Deprecated since version 1.4: The FromClause.select().whereclause
parameter is deprecated and will be removed in version 2.0. Please make use of the Select.where()
method to add WHERE criteria to the SELECT statement.
**kwargs¶ – additional keyword arguments are passed to the
legacy constructor for Select
described at
Select.create_legacy_select()
.
See also
select()
- general purpose
method which allows for arbitrary column lists.
sqlalchemy.sql.expression.FromClause.
table_valued()¶Return a TableValuedColumn
object for this
FromClause
.
A TableValuedColumn
is a ColumnElement
that
represents a complete row in a table. Support for this construct is
backend dependent, and is supported in various forms by backends
such as PostgreSQL, Oracle and SQL Server.
E.g.:
>>> from sqlalchemy import select, column, func, table
>>> a = table("a", column("id"), column("x"), column("y"))
>>> stmt = select(func.row_to_json(a.table_valued()))
>>> print(stmt)
SELECT row_to_json(a) AS row_to_json_1
FROM a
New in version 1.4.0b2.
See also
Working with SQL Functions - in the SQLAlchemy 1.4 / 2.0 Tutorial
sqlalchemy.sql.expression.FromClause.
tablesample(sampling, name=None, seed=None)¶Return a TABLESAMPLE alias of this FromClause
.
The return value is the TableSample
construct also
provided by the top-level tablesample()
function.
New in version 1.1.
See also
tablesample()
- usage guidelines and parameters
Base class for SELECT statements where additional elements can be added.
This serves as the base for Select
and
CompoundSelect
where elements such as ORDER BY, GROUP BY can be added and column
rendering can be controlled. Compare to
TextualSelect
, which,
while it subclasses SelectBase
and is also a SELECT construct,
represents a fixed textual string which cannot be altered at this level,
only wrapped as a subquery.
Class signature
class sqlalchemy.sql.expression.GenerativeSelect
(sqlalchemy.sql.expression.DeprecatedSelectBaseGenerations
, sqlalchemy.sql.expression.SelectBase
)
sqlalchemy.sql.expression.GenerativeSelect.
apply_labels()¶Deprecated since version 1.4: The GenerativeSelect.apply_labels()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Use set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL) instead. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.GenerativeSelect.
fetch(count, with_ties=False, percent=False)¶Return a new selectable with the given FETCH FIRST criterion applied.
This is a numeric value which usually renders as
FETCH {FIRST | NEXT} [ count ] {ROW | ROWS} {ONLY | WITH TIES}
expression in the resulting select. This functionality is
is currently implemented for Oracle, PostgreSQL, MSSQL.
Use GenerativeSelect.offset()
to specify the offset.
Note
The GenerativeSelect.fetch()
method will replace
any clause applied with GenerativeSelect.limit()
.
New in version 1.4.
count¶ – an integer COUNT parameter, or a SQL expression
that provides an integer result. When percent=True
this will
represent the percentage of rows to return, not the absolute value.
Pass None
to reset it.
with_ties¶ – When True
, the WITH TIES option is used
to return any additional rows that tie for the last place in the
result set according to the ORDER BY
clause. The
ORDER BY
may be mandatory in this case. Defaults to False
percent¶ – When True
, count
represents the percentage
of the total number of selected rows to return. Defaults to False
sqlalchemy.sql.expression.GenerativeSelect.
get_label_style()¶Retrieve the current label style.
New in version 1.4.
sqlalchemy.sql.expression.GenerativeSelect.
group_by(*clauses)¶Return a new selectable with the given list of GROUP BY criterion applied.
e.g.:
stmt = select(table.c.name, func.max(table.c.stat)).\
group_by(table.c.name)
*clauses¶ – a series of ColumnElement
constructs
which will be used to generate an GROUP BY clause.
sqlalchemy.sql.expression.GenerativeSelect.
limit(limit)¶Return a new selectable with the given LIMIT criterion applied.
This is a numerical value which usually renders as a LIMIT
expression in the resulting select. Backends that don’t
support LIMIT
will attempt to provide similar
functionality.
Note
The GenerativeSelect.limit()
method will replace
any clause applied with GenerativeSelect.fetch()
.
Changed in version 1.0.0: - Select.limit()
can now
accept arbitrary SQL expressions as well as integer values.
limit¶ – an integer LIMIT parameter, or a SQL expression
that provides an integer result. Pass None
to reset it.
sqlalchemy.sql.expression.GenerativeSelect.
offset(offset)¶Return a new selectable with the given OFFSET criterion applied.
This is a numeric value which usually renders as an OFFSET
expression in the resulting select. Backends that don’t
support OFFSET
will attempt to provide similar
functionality.
Changed in version 1.0.0: - Select.offset()
can now
accept arbitrary SQL expressions as well as integer values.
offset¶ – an integer OFFSET parameter, or a SQL expression
that provides an integer result. Pass None
to reset it.
sqlalchemy.sql.expression.GenerativeSelect.
order_by(*clauses)¶Return a new selectable with the given list of ORDER BY criterion applied.
e.g.:
stmt = select(table).order_by(table.c.id, table.c.name)
*clauses¶ – a series of ColumnElement
constructs
which will be used to generate an ORDER BY clause.
See also
ORDER BY - in the SQLAlchemy 1.4 / 2.0 Tutorial
Ordering or Grouping by a Label - in the SQLAlchemy 1.4 / 2.0 Tutorial
sqlalchemy.sql.expression.GenerativeSelect.
set_label_style(style)¶Return a new selectable with the specified label style.
There are three “label styles” available,
LABEL_STYLE_DISAMBIGUATE_ONLY
,
LABEL_STYLE_TABLENAME_PLUS_COL
, and
LABEL_STYLE_NONE
. The default style is
LABEL_STYLE_TABLENAME_PLUS_COL
.
In modern SQLAlchemy, there is not generally a need to change the
labeling style, as per-expression labels are more effectively used by
making use of the ColumnElement.label()
method. In past
versions, LABEL_STYLE_TABLENAME_PLUS_COL
was used to
disambiguate same-named columns from different tables, aliases, or
subqueries; the newer LABEL_STYLE_DISAMBIGUATE_ONLY
now
applies labels only to names that conflict with an existing name so
that the impact of this labeling is minimal.
The rationale for disambiguation is mostly so that all column
expressions are available from a given FromClause.c
collection when a subquery is created.
New in version 1.4: - the
GenerativeSelect.set_label_style()
method replaces the
previous combination of .apply_labels()
, .with_labels()
and
use_labels=True
methods and/or parameters.
sqlalchemy.sql.expression.GenerativeSelect.
slice(start, stop)¶Apply LIMIT / OFFSET to this statement based on a slice.
The start and stop indices behave like the argument to Python’s
built-in range()
function. This method provides an
alternative to using LIMIT
/OFFSET
to get a slice of the
query.
For example,
stmt = select(User).order_by(User).id.slice(1, 3)
renders as
SELECT users.id AS users_id,
users.name AS users_name
FROM users ORDER BY users.id
LIMIT ? OFFSET ?
(2, 1)
Note
The GenerativeSelect.slice()
method will replace
any clause applied with GenerativeSelect.fetch()
.
New in version 1.4: Added the GenerativeSelect.slice()
method generalized from the ORM.
sqlalchemy.sql.expression.GenerativeSelect.
with_for_update(nowait=False, read=False, of=None, skip_locked=False, key_share=False)¶Specify a FOR UPDATE
clause for this
GenerativeSelect
.
E.g.:
stmt = select(table).with_for_update(nowait=True)
On a database like PostgreSQL or Oracle, the above would render a statement like:
SELECT table.a, table.b FROM table FOR UPDATE NOWAIT
on other backends, the nowait
option is ignored and instead
would produce:
SELECT table.a, table.b FROM table FOR UPDATE
When called with no arguments, the statement will render with
the suffix FOR UPDATE
. Additional arguments can then be
provided which allow for common database-specific
variants.
nowait¶ – boolean; will render FOR UPDATE NOWAIT
on Oracle
and PostgreSQL dialects.
read¶ – boolean; will render LOCK IN SHARE MODE
on MySQL,
FOR SHARE
on PostgreSQL. On PostgreSQL, when combined with
nowait
, will render FOR SHARE NOWAIT
.
of¶ – SQL expression or list of SQL expression elements
(typically Column
objects or a compatible expression) which
will render into a FOR UPDATE OF
clause; supported by PostgreSQL
and Oracle. May render as a table or as a column depending on
backend.
skip_locked¶ – boolean, will render FOR UPDATE SKIP LOCKED
on Oracle and PostgreSQL dialects or FOR SHARE SKIP LOCKED
if
read=True
is also specified.
key_share¶ – boolean, will render FOR NO KEY UPDATE
,
or if combined with read=True
will render FOR KEY SHARE
,
on the PostgreSQL dialect.
Mixin that declares a class to include CTE support.
New in version 1.1.
Class signature
class sqlalchemy.sql.expression.HasCTE
(sqlalchemy.sql.roles.HasCTERole
)
sqlalchemy.sql.expression.HasCTE.
cte(name=None, recursive=False)¶Return a new CTE
,
or Common Table Expression instance.
Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
CTEs can also be applied to DML constructs UPDATE, INSERT and DELETE on some databases, both as a source of CTE rows when combined with RETURNING, as well as a consumer of CTE rows.
Changed in version 1.1: Added support for UPDATE/INSERT/DELETE as CTE, CTEs added to UPDATE/INSERT/DELETE.
SQLAlchemy detects CTE
objects, which are treated
similarly to Alias
objects, as special elements
to be delivered to the FROM clause of the statement as well
as to a WITH clause at the top of the statement.
For special prefixes such as PostgreSQL “MATERIALIZED” and
“NOT MATERIALIZED”, the CTE.prefix_with()
method may be
used to establish these.
Changed in version 1.3.13: Added support for prefixes. In particular - MATERIALIZED and NOT MATERIALIZED.
name¶ – name given to the common table expression. Like
FromClause.alias()
, the name can be left as
None
in which case an anonymous symbol will be used at query
compile time.
recursive¶ – if True
, will render WITH RECURSIVE
.
A recursive common table expression is intended to be used in
conjunction with UNION ALL in order to derive rows
from those already selected.
The following examples include two from PostgreSQL’s documentation at http://www.postgresql.org/docs/current/static/queries-with.html, as well as additional examples.
Example 1, non recursive:
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
orders = Table('orders', metadata,
Column('region', String),
Column('amount', Integer),
Column('product', String),
Column('quantity', Integer)
)
regional_sales = select(
orders.c.region,
func.sum(orders.c.amount).label('total_sales')
).group_by(orders.c.region).cte("regional_sales")
top_regions = select(regional_sales.c.region).\
where(
regional_sales.c.total_sales >
select(
func.sum(regional_sales.c.total_sales) / 10
)
).cte("top_regions")
statement = select(
orders.c.region,
orders.c.product,
func.sum(orders.c.quantity).label("product_units"),
func.sum(orders.c.amount).label("product_sales")
).where(orders.c.region.in_(
select(top_regions.c.region)
)).group_by(orders.c.region, orders.c.product)
result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
parts = Table('parts', metadata,
Column('part', String),
Column('sub_part', String),
Column('quantity', Integer),
)
included_parts = select(\
parts.c.sub_part, parts.c.part, parts.c.quantity\
).\
where(parts.c.part=='our part').\
cte(recursive=True)
incl_alias = included_parts.alias()
parts_alias = parts.alias()
included_parts = included_parts.union_all(
select(
parts_alias.c.sub_part,
parts_alias.c.part,
parts_alias.c.quantity
).\
where(parts_alias.c.part==incl_alias.c.sub_part)
)
statement = select(
included_parts.c.sub_part,
func.sum(included_parts.c.quantity).
label('total_quantity')
).\
group_by(included_parts.c.sub_part)
result = conn.execute(statement).fetchall()
Example 3, an upsert using UPDATE and INSERT with CTEs:
from datetime import date
from sqlalchemy import (MetaData, Table, Column, Integer,
Date, select, literal, and_, exists)
metadata = MetaData()
visitors = Table('visitors', metadata,
Column('product_id', Integer, primary_key=True),
Column('date', Date, primary_key=True),
Column('count', Integer),
)
# add 5 visitors for the product_id == 1
product_id = 1
day = date.today()
count = 5
update_cte = (
visitors.update()
.where(and_(visitors.c.product_id == product_id,
visitors.c.date == day))
.values(count=visitors.c.count + count)
.returning(literal(1))
.cte('update_cte')
)
upsert = visitors.insert().from_select(
[visitors.c.product_id, visitors.c.date, visitors.c.count],
select(literal(product_id), literal(day), literal(count))
.where(~exists(update_cte.select()))
)
connection.execute(upsert)
See also
Query.cte()
- ORM version of
HasCTE.cte()
.
sqlalchemy.sql.expression.HasPrefixes.
prefix_with(*expr, **kw)¶Add one or more expressions following the statement keyword, i.e. SELECT, INSERT, UPDATE, or DELETE. Generative.
This is used to support backend-specific prefix keywords such as those provided by MySQL.
E.g.:
stmt = table.insert().prefix_with("LOW_PRIORITY", dialect="mysql")
# MySQL 5.7 optimizer hints
stmt = select(table).prefix_with(
"/*+ BKA(t1) */", dialect="mysql")
Multiple prefixes can be specified by multiple calls
to HasPrefixes.prefix_with()
.
*expr¶ – textual or ClauseElement
construct which
will be rendered following the INSERT, UPDATE, or DELETE
keyword.
**kw¶ – A single keyword ‘dialect’ is accepted. This is an optional string dialect name which will limit rendering of this prefix to only that dialect.
sqlalchemy.sql.expression.HasSuffixes.
suffix_with(*expr, **kw)¶Add one or more expressions following the statement as a whole.
This is used to support backend-specific suffix keywords on certain constructs.
E.g.:
stmt = select(col1, col2).cte().suffix_with(
"cycle empno set y_cycle to 1 default 0", dialect="oracle")
Multiple suffixes can be specified by multiple calls
to HasSuffixes.suffix_with()
.
*expr¶ – textual or ClauseElement
construct which
will be rendered following the target clause.
**kw¶ – A single keyword ‘dialect’ is accepted. This is an optional string dialect name which will limit rendering of this suffix to only that dialect.
Represent a JOIN
construct between two
FromClause
elements.
The public constructor function for Join
is the module-level
join()
function, as well as the
FromClause.join()
method
of any FromClause
(e.g. such as
Table
).
Class signature
class sqlalchemy.sql.expression.Join
(sqlalchemy.sql.roles.DMLTableRole
, sqlalchemy.sql.expression.FromClause
)
sqlalchemy.sql.expression.Join.
__init__(left, right, onclause=None, isouter=False, full=False)¶Construct a new Join
.
The usual entrypoint here is the join()
function or the FromClause.join()
method of any
FromClause
object.
sqlalchemy.sql.expression.Join.
alias(name=None, flat=False)¶Return an alias of this Join
.
Deprecated since version 1.4: The Join.alias()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Create a select + subquery, or alias the individual tables inside the join, instead. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
The default behavior here is to first produce a SELECT
construct from this Join
, then to produce an
Alias
from that. So given a join of the form:
j = table_a.join(table_b, table_a.c.id == table_b.c.a_id)
The JOIN by itself would look like:
table_a JOIN table_b ON table_a.id = table_b.a_id
Whereas the alias of the above, j.alias()
, would in a
SELECT context look like:
(SELECT table_a.id AS table_a_id, table_b.id AS table_b_id,
table_b.a_id AS table_b_a_id
FROM table_a
JOIN table_b ON table_a.id = table_b.a_id) AS anon_1
The equivalent long-hand form, given a Join
object j
, is:
from sqlalchemy import select, alias
j = alias(
select(j.left, j.right).\
select_from(j).\
set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL).\
correlate(False),
name=name
)
The selectable produced by Join.alias()
features the same
columns as that of the two individual selectables presented under
a single name - the individual columns are “auto-labeled”, meaning
the .c.
collection of the resulting Alias
represents
the names of the individual columns using a
<tablename>_<columname>
scheme:
j.c.table_a_id
j.c.table_b_a_id
Join.alias()
also features an alternate
option for aliasing joins which produces no enclosing SELECT and
does not normally apply labels to the column names. The
flat=True
option will call FromClause.alias()
against the left and right sides individually.
Using this option, no new SELECT
is produced;
we instead, from a construct as below:
j = table_a.join(table_b, table_a.c.id == table_b.c.a_id)
j = j.alias(flat=True)
we get a result like this:
table_a AS table_a_1 JOIN table_b AS table_b_1 ON
table_a_1.id = table_b_1.a_id
The flat=True
argument is also propagated to the contained
selectables, so that a composite join such as:
j = table_a.join(
table_b.join(table_c,
table_b.c.id == table_c.c.b_id),
table_b.c.a_id == table_a.c.id
).alias(flat=True)
Will produce an expression like:
table_a AS table_a_1 JOIN (
table_b AS table_b_1 JOIN table_c AS table_c_1
ON table_b_1.id = table_c_1.b_id
) ON table_a_1.id = table_b_1.a_id
The standalone alias()
function as well as the
base FromClause.alias()
method also support the flat=True
argument as a no-op, so that the argument can be passed to the
alias()
method of any selectable.
sqlalchemy.sql.expression.Join.
bind¶Return the bound engine associated with either the left or right
side of this Join
.
Deprecated since version 1.4: The Executable.bind
attribute is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Bound metadata is being removed as of SQLAlchemy 2.0. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.Join.
description¶sqlalchemy.sql.expression.Join.
is_derived_from(fromclause)¶Return True
if this FromClause
is
‘derived’ from the given FromClause
.
An example would be an Alias of a Table is derived from that Table.
sqlalchemy.sql.expression.Join.
select(whereclause=None, **kwargs)¶Create a Select
from this
Join
.
E.g.:
stmt = table_a.join(table_b, table_a.c.id == table_b.c.a_id)
stmt = stmt.select()
The above will produce a SQL string resembling:
SELECT table_a.id, table_a.col, table_b.id, table_b.a_id
FROM table_a JOIN table_b ON table_a.id = table_b.a_id
whereclause¶ –
WHERE criteria, same as calling
Select.where()
on the resulting statement
Deprecated since version 1.4: The Join.select().whereclause
parameter is deprecated and will be removed in version 2.0. Please make use of the Select.where()
method to add WHERE criteria to the SELECT statement.
**kwargs¶ – additional keyword arguments are passed to the
legacy constructor for Select
described at
Select.create_legacy_select()
.
sqlalchemy.sql.expression.Join.
self_group(against=None)¶Apply a ‘grouping’ to this ClauseElement
.
This method is overridden by subclasses to return a “grouping”
construct, i.e. parenthesis. In particular it’s used by “binary”
expressions to provide a grouping around themselves when placed into a
larger expression, as well as by select()
constructs when placed into the FROM clause of another
select()
. (Note that subqueries should be
normally created using the Select.alias()
method,
as many
platforms require nested SELECT statements to be named).
As expressions are composed together, the application of
self_group()
is automatic - end-user code should never
need to use this method directly. Note that SQLAlchemy’s
clause constructs take operator precedence into account -
so parenthesis might not be needed, for example, in
an expression like x OR (y AND z)
- AND takes precedence
over OR.
The base self_group()
method of
ClauseElement
just returns self.
Represent a LATERAL subquery.
This object is constructed from the lateral()
module
level function as well as the FromClause.lateral()
method available
on all FromClause
subclasses.
While LATERAL is part of the SQL standard, currently only more recent PostgreSQL versions provide support for this keyword.
New in version 1.1.
See also
LATERAL correlation - overview of usage.
Class signature
class sqlalchemy.sql.expression.Lateral
(sqlalchemy.sql.expression.AliasedReturnsRows
)
The base-most class for Core constructs that have some concept of columns that can represent rows.
While the SELECT statement and TABLE are the primary things we think of in this category, DML like INSERT, UPDATE and DELETE can also specify RETURNING which means they can be used in CTEs and other forms, and PostgreSQL has functions that return rows also.
New in version 1.4.
Class signature
class sqlalchemy.sql.expression.ReturnsRows
(sqlalchemy.sql.roles.ReturnsRowsRole
, sqlalchemy.sql.expression.ClauseElement
)
sqlalchemy.sql.expression.ReturnsRows.
exported_columns¶A ColumnCollection
that represents the “exported”
columns of this ReturnsRows
.
The “exported” columns represent the collection of
ColumnElement
expressions that are rendered by this SQL
construct. There are primary varieties which are the
“FROM clause columns” of a FROM clause, such as a table, join,
or subquery, the “SELECTed columns”, which are the columns in
the “columns clause” of a SELECT statement, and the RETURNING
columns in a DML statement..
New in version 1.4.
Represent a scalar subquery.
A ScalarSelect
is created by invoking the
SelectBase.scalar_subquery()
method. The object
then participates in other SQL expressions as a SQL column expression
within the ColumnElement
hierarchy.
See also
Scalar and Correlated Subqueries - in the 2.0 tutorial
Scalar Selects - in the 1.x tutorial
Class signature
class sqlalchemy.sql.expression.ScalarSelect
(sqlalchemy.sql.roles.InElementRole
, sqlalchemy.sql.expression.Generative
, sqlalchemy.sql.expression.Grouping
)
sqlalchemy.sql.expression.ScalarSelect.
correlate(*fromclauses)¶Return a new ScalarSelect
which will correlate the given FROM
clauses to that of an enclosing Select
.
This method is mirrored from the Select.correlate()
method
of the underlying Select
. The method applies the
:meth:_sql.Select.correlate` method, then returns a new
ScalarSelect
against that statement.
New in version 1.4: Previously, the
ScalarSelect.correlate()
method was only available from Select
.
*fromclauses¶ – a list of one or more
FromClause
constructs, or other compatible constructs (i.e. ORM-mapped
classes) to become part of the correlate collection.
See also
ScalarSelect.correlate_except()
Scalar and Correlated Subqueries - in the 2.0 tutorial
Correlated Subqueries - in the 1.x tutorial
sqlalchemy.sql.expression.ScalarSelect.
correlate_except(*fromclauses)¶Return a new ScalarSelect
which will omit the given FROM
clauses from the auto-correlation process.
This method is mirrored from the
Select.correlate_except()
method of the underlying
Select
. The method applies the
:meth:_sql.Select.correlate_except` method, then returns a new
ScalarSelect
against that statement.
New in version 1.4: Previously, the
ScalarSelect.correlate_except()
method was only available from Select
.
*fromclauses¶ – a list of one or more
FromClause
constructs, or other compatible constructs (i.e. ORM-mapped
classes) to become part of the correlate-exception collection.
See also
Scalar and Correlated Subqueries - in the 2.0 tutorial
Correlated Subqueries - in the 1.x tutorial
sqlalchemy.sql.expression.ScalarSelect.
self_group(**kwargs)¶Apply a ‘grouping’ to this ClauseElement
.
This method is overridden by subclasses to return a “grouping”
construct, i.e. parenthesis. In particular it’s used by “binary”
expressions to provide a grouping around themselves when placed into a
larger expression, as well as by select()
constructs when placed into the FROM clause of another
select()
. (Note that subqueries should be
normally created using the Select.alias()
method,
as many
platforms require nested SELECT statements to be named).
As expressions are composed together, the application of
self_group()
is automatic - end-user code should never
need to use this method directly. Note that SQLAlchemy’s
clause constructs take operator precedence into account -
so parenthesis might not be needed, for example, in
an expression like x OR (y AND z)
- AND takes precedence
over OR.
The base self_group()
method of
ClauseElement
just returns self.
sqlalchemy.sql.expression.ScalarSelect.
where(crit)¶Apply a WHERE clause to the SELECT statement referred to
by this ScalarSelect
.
Represents a SELECT
statement.
The Select
object is normally constructed using the
select()
function. See that function for details.
Class signature
class sqlalchemy.sql.expression.Select
(sqlalchemy.sql.expression.HasPrefixes
, sqlalchemy.sql.expression.HasSuffixes
, sqlalchemy.sql.expression.HasHints
, sqlalchemy.sql.expression.HasCompileState
, sqlalchemy.sql.expression.DeprecatedSelectGenerations
, sqlalchemy.sql.expression._SelectFromElements
, sqlalchemy.sql.expression.GenerativeSelect
)
sqlalchemy.sql.expression.Select.
add_columns(*columns)¶Return a new select()
construct with
the given column expressions added to its columns clause.
E.g.:
my_select = my_select.add_columns(table.c.new_column)
See the documentation for
Select.with_only_columns()
for guidelines on adding /replacing the columns of a
Select
object.
sqlalchemy.sql.expression.Select.
alias(name=None, flat=False)¶inherited from the SelectBase.alias()
method of SelectBase
Return a named subquery against this
SelectBase
.
For a SelectBase
(as opposed to a
FromClause
),
this returns a Subquery
object which behaves mostly the
same as the Alias
object that is used with a
FromClause
.
Changed in version 1.4: The SelectBase.alias()
method is now
a synonym for the SelectBase.subquery()
method.
sqlalchemy.sql.expression.Select.
apply_labels()¶inherited from the GenerativeSelect.apply_labels()
method of GenerativeSelect
Deprecated since version 1.4: The GenerativeSelect.apply_labels()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Use set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL) instead. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.Select.
as_scalar()¶inherited from the SelectBase.as_scalar()
method of SelectBase
Deprecated since version 1.4: The SelectBase.as_scalar()
method is deprecated and will be removed in a future release. Please refer to SelectBase.scalar_subquery()
.
sqlalchemy.sql.expression.Select.
bind¶Returns the Engine
or Connection
to which this Executable
is bound, or None if none found.
Deprecated since version 1.4: The Executable.bind
attribute is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Bound metadata is being removed as of SQLAlchemy 2.0. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.Select.
c¶inherited from the SelectBase.c
attribute of SelectBase
Deprecated since version 1.4: The SelectBase.c
and SelectBase.columns
attributes are deprecated and will be removed in a future release; these attributes implicitly create a subquery that should be explicit. Please call SelectBase.subquery()
first in order to create a subquery, which then contains this attribute. To access the columns that this SELECT object SELECTs from, use the SelectBase.selected_columns
attribute.
sqlalchemy.sql.expression.Select.
column(column)¶Return a new select()
construct with
the given column expression added to its columns clause.
Deprecated since version 1.4: The Select.column()
method is deprecated and will be removed in a future release. Please use Select.add_columns()
E.g.:
my_select = my_select.column(table.c.new_column)
See the documentation for
Select.with_only_columns()
for guidelines on adding /replacing the columns of a
Select
object.
sqlalchemy.sql.expression.Select.
column_descriptions¶Return a ‘column descriptions’ structure which may be plugin-specific.
sqlalchemy.sql.expression.Select.
correlate(*fromclauses)¶Return a new Select
which will correlate the given FROM
clauses to that of an enclosing Select
.
Calling this method turns off the Select
object’s
default behavior of “auto-correlation”. Normally, FROM elements
which appear in a Select
that encloses this one via
its WHERE clause, ORDER BY, HAVING or
columns clause will be omitted from this
Select
object’s FROM clause.
Setting an explicit correlation collection using the
Select.correlate()
method provides a fixed list of FROM objects
that can potentially take place in this process.
When Select.correlate()
is used to apply specific FROM clauses
for correlation, the FROM elements become candidates for
correlation regardless of how deeply nested this
Select
object is, relative to an enclosing Select
which refers to
the same FROM object. This is in contrast to the behavior of
“auto-correlation” which only correlates to an immediate enclosing
Select
.
Multi-level correlation ensures that the link
between enclosed and enclosing Select
is always via
at least one WHERE/ORDER BY/HAVING/columns clause in order for
correlation to take place.
If None
is passed, the Select
object will correlate
none of its FROM entries, and all will render unconditionally
in the local FROM clause.
*fromclauses¶ – a list of one or more
FromClause
constructs, or other compatible constructs (i.e. ORM-mapped
classes) to become part of the correlate collection.
sqlalchemy.sql.expression.Select.
correlate_except(*fromclauses)¶Return a new Select
which will omit the given FROM
clauses from the auto-correlation process.
Calling Select.correlate_except()
turns off the
Select
object’s default behavior of
“auto-correlation” for the given FROM elements. An element
specified here will unconditionally appear in the FROM list, while
all other FROM elements remain subject to normal auto-correlation
behaviors.
If None
is passed, the Select
object will correlate
all of its FROM entries.
*fromclauses¶ – a list of one or more
FromClause
constructs, or other compatible constructs (i.e. ORM-mapped
classes) to become part of the correlate-exception collection.
sqlalchemy.sql.expression.Select.
corresponding_column(column, require_embedded=False)¶inherited from the Selectable.corresponding_column()
method of Selectable
Given a ColumnElement
, return the exported
ColumnElement
object from the
Selectable.exported_columns
collection of this Selectable
which corresponds to that
original ColumnElement
via a common ancestor
column.
column¶ – the target ColumnElement
to be matched.
require_embedded¶ – only return corresponding columns for
the given ColumnElement
, if the given
ColumnElement
is actually present within a sub-element
of this Selectable
.
Normally the column will match if
it merely shares a common ancestor with one of the exported
columns of this Selectable
.
See also
Selectable.exported_columns
- the
ColumnCollection
that is used for the operation.
ColumnCollection.corresponding_column()
- implementation
method.
sqlalchemy.sql.expression.Select.
classmethod create_legacy_select(columns=None, whereclause=None, from_obj=None, distinct=False, having=None, correlate=True, prefixes=None, suffixes=None, **kwargs)¶Construct a new Select
using the 1.x style API.
Deprecated since version 1.4: The legacy calling style of select()
is deprecated and will be removed in SQLAlchemy 2.0. Please use the new calling style described at select()
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
This method is called implicitly when the select()
construct is used and the first argument is a Python list or other
plain sequence object, which is taken to refer to the columns
collection.
Changed in version 1.4: Added the Select.create_legacy_select()
constructor which documents the calling style in use when the
select()
construct is invoked using 1.x-style arguments.
Similar functionality is also available via the
FromClause.select()
method on any
FromClause
.
All arguments which accept ClauseElement
arguments
also accept string arguments, which will be converted as appropriate
into either text()
or
literal_column()
constructs.
columns¶ –
A list of ColumnElement
or
FromClause
objects which will form the columns clause of the resulting
statement. For those objects that are instances of
FromClause
(typically Table
or Alias
objects), the FromClause.c
collection is extracted
to form a collection of ColumnElement
objects.
This parameter will also accept TextClause
constructs as
given, as well as ORM-mapped classes.
Note
The select.columns
parameter is not available
in the method form of select()
, e.g.
FromClause.select()
.
whereclause¶ –
A ClauseElement
expression which will be used to form the
WHERE
clause. It is typically preferable to add WHERE
criterion to an existing Select
using method chaining
with Select.where()
.
See also
from_obj¶ –
A list of ClauseElement
objects which will be added to the
FROM
clause of the resulting statement. This is equivalent
to calling Select.select_from()
using method chaining on
an existing Select
object.
See also
Select.select_from()
- full description of explicit
FROM clause specification.
bind=None¶ – an Engine
or Connection
instance
to which the
resulting Select
object will be bound. The
Select
object will otherwise automatically bind to
whatever Connectable
instances can be located within
its contained ClauseElement
members.
correlate=True¶ –
indicates that this Select
object should have its
contained FromClause
elements “correlated” to an enclosing
Select
object.
It is typically preferable to specify
correlations on an existing Select
construct using
Select.correlate()
.
See also
Select.correlate()
- full description of correlation.
distinct=False¶ –
when True
, applies a DISTINCT
qualifier to the columns
clause of the resulting statement.
The boolean argument may also be a column expression or list
of column expressions - this is a special calling form which
is understood by the PostgreSQL dialect to render the
DISTINCT ON (<columns>)
syntax.
distinct
is also available on an existing
Select
object via the Select.distinct()
method.
See also
group_by¶ –
a list of ClauseElement
objects which will comprise the
GROUP BY
clause of the resulting select. This parameter
is typically specified more naturally using the
Select.group_by()
method on an existing
Select
.
See also
having¶ –
a ClauseElement
that will comprise the HAVING
clause
of the resulting select when GROUP BY
is used. This parameter
is typically specified more naturally using the
Select.having()
method on an existing
Select
.
See also
limit=None¶ –
a numerical value which usually renders as a LIMIT
expression in the resulting select. Backends that don’t
support LIMIT
will attempt to provide similar
functionality. This parameter is typically specified more
naturally using the Select.limit()
method on an existing
Select
.
See also
offset=None¶ –
a numeric value which usually renders as an OFFSET
expression in the resulting select. Backends that don’t
support OFFSET
will attempt to provide similar
functionality. This parameter is typically specified more naturally
using the Select.offset()
method on an existing
Select
.
See also
order_by¶ –
a scalar or list of ClauseElement
objects which will
comprise the ORDER BY
clause of the resulting select.
This parameter is typically specified more naturally using the
Select.order_by()
method on an existing
Select
.
See also
use_labels=False¶ –
when True
, the statement will be generated using labels
for each column in the columns clause, which qualify each
column with its parent table’s (or aliases) name so that name
conflicts between columns in different tables don’t occur.
The format of the label is <tablename>_<column>
. The “c”
collection of a Subquery
created
against this Select
object, as well as the Select.selected_columns
collection of the Select
itself, will use these
names for targeting column members.
This parameter can also be specified on an existing
Select
object using the
Select.set_label_style()
method.
See also
sqlalchemy.sql.expression.Select.
cte(name=None, recursive=False)¶inherited from the HasCTE.cte()
method of HasCTE
Return a new CTE
,
or Common Table Expression instance.
Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
CTEs can also be applied to DML constructs UPDATE, INSERT and DELETE on some databases, both as a source of CTE rows when combined with RETURNING, as well as a consumer of CTE rows.
Changed in version 1.1: Added support for UPDATE/INSERT/DELETE as CTE, CTEs added to UPDATE/INSERT/DELETE.
SQLAlchemy detects CTE
objects, which are treated
similarly to Alias
objects, as special elements
to be delivered to the FROM clause of the statement as well
as to a WITH clause at the top of the statement.
For special prefixes such as PostgreSQL “MATERIALIZED” and
“NOT MATERIALIZED”, the CTE.prefix_with()
method may be
used to establish these.
Changed in version 1.3.13: Added support for prefixes. In particular - MATERIALIZED and NOT MATERIALIZED.
name¶ – name given to the common table expression. Like
FromClause.alias()
, the name can be left as
None
in which case an anonymous symbol will be used at query
compile time.
recursive¶ – if True
, will render WITH RECURSIVE
.
A recursive common table expression is intended to be used in
conjunction with UNION ALL in order to derive rows
from those already selected.
The following examples include two from PostgreSQL’s documentation at http://www.postgresql.org/docs/current/static/queries-with.html, as well as additional examples.
Example 1, non recursive:
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
orders = Table('orders', metadata,
Column('region', String),
Column('amount', Integer),
Column('product', String),
Column('quantity', Integer)
)
regional_sales = select(
orders.c.region,
func.sum(orders.c.amount).label('total_sales')
).group_by(orders.c.region).cte("regional_sales")
top_regions = select(regional_sales.c.region).\
where(
regional_sales.c.total_sales >
select(
func.sum(regional_sales.c.total_sales) / 10
)
).cte("top_regions")
statement = select(
orders.c.region,
orders.c.product,
func.sum(orders.c.quantity).label("product_units"),
func.sum(orders.c.amount).label("product_sales")
).where(orders.c.region.in_(
select(top_regions.c.region)
)).group_by(orders.c.region, orders.c.product)
result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
parts = Table('parts', metadata,
Column('part', String),
Column('sub_part', String),
Column('quantity', Integer),
)
included_parts = select(\
parts.c.sub_part, parts.c.part, parts.c.quantity\
).\
where(parts.c.part=='our part').\
cte(recursive=True)
incl_alias = included_parts.alias()
parts_alias = parts.alias()
included_parts = included_parts.union_all(
select(
parts_alias.c.sub_part,
parts_alias.c.part,
parts_alias.c.quantity
).\
where(parts_alias.c.part==incl_alias.c.sub_part)
)
statement = select(
included_parts.c.sub_part,
func.sum(included_parts.c.quantity).
label('total_quantity')
).\
group_by(included_parts.c.sub_part)
result = conn.execute(statement).fetchall()
Example 3, an upsert using UPDATE and INSERT with CTEs:
from datetime import date
from sqlalchemy import (MetaData, Table, Column, Integer,
Date, select, literal, and_, exists)
metadata = MetaData()
visitors = Table('visitors', metadata,
Column('product_id', Integer, primary_key=True),
Column('date', Date, primary_key=True),
Column('count', Integer),
)
# add 5 visitors for the product_id == 1
product_id = 1
day = date.today()
count = 5
update_cte = (
visitors.update()
.where(and_(visitors.c.product_id == product_id,
visitors.c.date == day))
.values(count=visitors.c.count + count)
.returning(literal(1))
.cte('update_cte')
)
upsert = visitors.insert().from_select(
[visitors.c.product_id, visitors.c.date, visitors.c.count],
select(literal(product_id), literal(day), literal(count))
.where(~exists(update_cte.select()))
)
connection.execute(upsert)
See also
Query.cte()
- ORM version of
HasCTE.cte()
.
sqlalchemy.sql.expression.Select.
distinct(*expr)¶Return a new select()
construct which
will apply DISTINCT to its columns clause.
*expr¶ –
optional column expressions. When present,
the PostgreSQL dialect will render a DISTINCT ON (<expressions>>)
construct.
Deprecated since version 1.4: Using *expr in other dialects is deprecated
and will raise CompileError
in a future version.
sqlalchemy.sql.expression.Select.
except_(other, **kwargs)¶Return a SQL EXCEPT
of this select() construct against
the given selectable.
sqlalchemy.sql.expression.Select.
except_all(other, **kwargs)¶Return a SQL EXCEPT ALL
of this select() construct against
the given selectable.
sqlalchemy.sql.expression.Select.
execute(*multiparams, **params)¶inherited from the Executable.execute()
method of Executable
Compile and execute this Executable
.
Deprecated since version 1.4: The Executable.execute()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. All statement execution in SQLAlchemy 2.0 is performed by the Connection.execute()
method of Connection
, or in the ORM by the Session.execute()
method of Session
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.Select.
execution_options(**kw)¶inherited from the Executable.execution_options()
method of Executable
Set non-SQL options for the statement which take effect during execution.
Execution options can be set on a per-statement or
per Connection
basis. Additionally, the
Engine
and ORM Query
objects provide
access to execution options which they in turn configure upon
connections.
The execution_options()
method is generative. A new
instance of this statement is returned that contains the options:
statement = select(table.c.x, table.c.y)
statement = statement.execution_options(autocommit=True)
Note that only a subset of possible execution options can be applied
to a statement - these include “autocommit” and “stream_results”,
but not “isolation_level” or “compiled_cache”.
See Connection.execution_options()
for a full list of
possible options.
sqlalchemy.sql.expression.Select.
exists()¶inherited from the SelectBase.exists()
method of SelectBase
Return an Exists
representation of this selectable,
which can be used as a column expression.
The returned object is an instance of Exists
.
New in version 1.4.
sqlalchemy.sql.expression.Select.
exported_columns¶inherited from the SelectBase.exported_columns
attribute of SelectBase
A ColumnCollection
that represents the “exported”
columns of this Selectable
, not including
TextClause
constructs.
The “exported” columns for a SelectBase
object are synonymous
with the SelectBase.selected_columns
collection.
New in version 1.4.
sqlalchemy.sql.expression.Select.
fetch(count, with_ties=False, percent=False)¶inherited from the GenerativeSelect.fetch()
method of GenerativeSelect
Return a new selectable with the given FETCH FIRST criterion applied.
This is a numeric value which usually renders as
FETCH {FIRST | NEXT} [ count ] {ROW | ROWS} {ONLY | WITH TIES}
expression in the resulting select. This functionality is
is currently implemented for Oracle, PostgreSQL, MSSQL.
Use GenerativeSelect.offset()
to specify the offset.
Note
The GenerativeSelect.fetch()
method will replace
any clause applied with GenerativeSelect.limit()
.
New in version 1.4.
count¶ – an integer COUNT parameter, or a SQL expression
that provides an integer result. When percent=True
this will
represent the percentage of rows to return, not the absolute value.
Pass None
to reset it.
with_ties¶ – When True
, the WITH TIES option is used
to return any additional rows that tie for the last place in the
result set according to the ORDER BY
clause. The
ORDER BY
may be mandatory in this case. Defaults to False
percent¶ – When True
, count
represents the percentage
of the total number of selected rows to return. Defaults to False
sqlalchemy.sql.expression.Select.
filter(*criteria)¶A synonym for the Select.where()
method.
sqlalchemy.sql.expression.Select.
filter_by(**kwargs)¶apply the given filtering criterion as a WHERE clause to this select.
sqlalchemy.sql.expression.Select.
from_statement(statement)¶Apply the columns which this Select
would select
onto another statement.
This operation is plugin-specific and will raise a not
supported exception if this Select
does not select from
plugin-enabled entities.
The statement is typically either a text()
or
select()
construct, and should return the set of
columns appropriate to the entities represented by this
Select
.
See also
Getting ORM Results from Textual and Core Statements - usage examples in the ORM Querying Guide
sqlalchemy.sql.expression.Select.
froms¶Return the displayed list of FromClause
elements.
sqlalchemy.sql.expression.Select.
get_children(**kwargs)¶Return immediate child Traversible
elements of this Traversible
.
This is used for visit traversal.
**kw may contain flags that change the collection that is returned, for example to return a subset of items in order to cut down on larger traversals, or to return child items from a different context (such as schema-level collections instead of clause-level).
sqlalchemy.sql.expression.Select.
get_execution_options()¶inherited from the Executable.get_execution_options()
method of Executable
Get the non-SQL options which will take effect during execution.
New in version 1.3.
See also
sqlalchemy.sql.expression.Select.
get_label_style()¶inherited from the GenerativeSelect.get_label_style()
method of GenerativeSelect
Retrieve the current label style.
New in version 1.4.
sqlalchemy.sql.expression.Select.
group_by(*clauses)¶inherited from the GenerativeSelect.group_by()
method of GenerativeSelect
Return a new selectable with the given list of GROUP BY criterion applied.
e.g.:
stmt = select(table.c.name, func.max(table.c.stat)).\
group_by(table.c.name)
*clauses¶ – a series of ColumnElement
constructs
which will be used to generate an GROUP BY clause.
sqlalchemy.sql.expression.Select.
having(having)¶Return a new select()
construct with
the given expression added to
its HAVING clause, joined to the existing clause via AND, if any.
sqlalchemy.sql.expression.Select.
inner_columns¶An iterator of all ColumnElement
expressions which would
be rendered into the columns clause of the resulting SELECT statement.
This method is legacy as of 1.4 and is superseded by the
Select.exported_columns
collection.
sqlalchemy.sql.expression.Select.
intersect(other, **kwargs)¶Return a SQL INTERSECT
of this select() construct against
the given selectable.
sqlalchemy.sql.expression.Select.
intersect_all(other, **kwargs)¶Return a SQL INTERSECT ALL
of this select() construct
against the given selectable.
sqlalchemy.sql.expression.Select.
join(target, onclause=None, isouter=False, full=False)¶Create a SQL JOIN against this Select
object’s criterion
and apply generatively, returning the newly resulting
Select
.
E.g.:
stmt = select(user_table).join(address_table, user_table.c.id == address_table.c.user_id)
The above statement generates SQL similar to:
SELECT user.id, user.name FROM user JOIN address ON user.id = address.user_id
Changed in version 1.4: Select.join()
now creates
a Join
object between a FromClause
source that is within the FROM clause of the existing SELECT,
and a given target FromClause
, and then adds
this Join
to the FROM clause of the newly generated
SELECT statement. This is completely reworked from the behavior
in 1.3, which would instead create a subquery of the entire
Select
and then join that subquery to the
target.
This is a backwards incompatible change as the previous behavior
was mostly useless, producing an unnamed subquery rejected by
most databases in any case. The new behavior is modeled after
that of the very successful Query.join()
method in the
ORM, in order to support the functionality of Query
being available by using a Select
object with an
Session
.
See the notes for this change at select().join() and outerjoin() add JOIN criteria to the current query, rather than creating a subquery.
target¶ – target table to join towards
onclause¶ – ON clause of the join. If omitted, an ON clause
is generated automatically based on the ForeignKey
linkages between the two tables, if one can be unambiguously
determined, otherwise an error is raised.
isouter¶ – if True, generate LEFT OUTER join. Same as
Select.outerjoin()
.
full¶ – if True, generate FULL OUTER join.
See also
Explicit FROM clauses and JOINs - in the SQLAlchemy 1.4 / 2.0 Tutorial
Joins - in the ORM Querying Guide
sqlalchemy.sql.expression.Select.
join_from(from_, target, onclause=None, isouter=False, full=False)¶Create a SQL JOIN against this Select
object’s criterion
and apply generatively, returning the newly resulting
Select
.
E.g.:
stmt = select(user_table, address_table).join_from(
user_table, address_table, user_table.c.id == address_table.c.user_id
)
The above statement generates SQL similar to:
SELECT user.id, user.name, address.id, address.email, address.user_id
FROM user JOIN address ON user.id = address.user_id
New in version 1.4.
from_¶ – the left side of the join, will be rendered in the
FROM clause and is roughly equivalent to using the
Select.select_from()
method.
target¶ – target table to join towards
onclause¶ – ON clause of the join.
isouter¶ – if True, generate LEFT OUTER join. Same as
Select.outerjoin()
.
full¶ – if True, generate FULL OUTER join.
See also
Explicit FROM clauses and JOINs - in the SQLAlchemy 1.4 / 2.0 Tutorial
Joins - in the ORM Querying Guide
sqlalchemy.sql.expression.Select.
label(name)¶inherited from the SelectBase.label()
method of SelectBase
Return a ‘scalar’ representation of this selectable, embedded as a subquery with a label.
See also
sqlalchemy.sql.expression.Select.
lateral(name=None)¶inherited from the SelectBase.lateral()
method of SelectBase
Return a LATERAL alias of this Selectable
.
The return value is the Lateral
construct also
provided by the top-level lateral()
function.
New in version 1.1.
See also
LATERAL correlation - overview of usage.
sqlalchemy.sql.expression.Select.
limit(limit)¶inherited from the GenerativeSelect.limit()
method of GenerativeSelect
Return a new selectable with the given LIMIT criterion applied.
This is a numerical value which usually renders as a LIMIT
expression in the resulting select. Backends that don’t
support LIMIT
will attempt to provide similar
functionality.
Note
The GenerativeSelect.limit()
method will replace
any clause applied with GenerativeSelect.fetch()
.
Changed in version 1.0.0: - Select.limit()
can now
accept arbitrary SQL expressions as well as integer values.
limit¶ – an integer LIMIT parameter, or a SQL expression
that provides an integer result. Pass None
to reset it.
sqlalchemy.sql.expression.Select.
offset(offset)¶inherited from the GenerativeSelect.offset()
method of GenerativeSelect
Return a new selectable with the given OFFSET criterion applied.
This is a numeric value which usually renders as an OFFSET
expression in the resulting select. Backends that don’t
support OFFSET
will attempt to provide similar
functionality.
Changed in version 1.0.0: - Select.offset()
can now
accept arbitrary SQL expressions as well as integer values.
offset¶ – an integer OFFSET parameter, or a SQL expression
that provides an integer result. Pass None
to reset it.
sqlalchemy.sql.expression.Select.
options(*options)¶inherited from the Executable.options()
method of Executable
Apply options to this statement.
In the general sense, options are any kind of Python object that can be interpreted by the SQL compiler for the statement. These options can be consumed by specific dialects or specific kinds of compilers.
The most commonly known kind of option are the ORM level options that apply “eager load” and other loading behaviors to an ORM query. However, options can theoretically be used for many other purposes.
For background on specific kinds of options for specific kinds of statements, refer to the documentation for those option objects.
Changed in version 1.4: - added Generative.options()
to
Core statement objects towards the goal of allowing unified
Core / ORM querying capabilities.
See also
Deferred Column Loader Query Options - refers to options specific to the usage of ORM queries
Relationship Loading with Loader Options - refers to options specific to the usage of ORM queries
sqlalchemy.sql.expression.Select.
order_by(*clauses)¶inherited from the GenerativeSelect.order_by()
method of GenerativeSelect
Return a new selectable with the given list of ORDER BY criterion applied.
e.g.:
stmt = select(table).order_by(table.c.id, table.c.name)
*clauses¶ – a series of ColumnElement
constructs
which will be used to generate an ORDER BY clause.
See also
ORDER BY - in the SQLAlchemy 1.4 / 2.0 Tutorial
Ordering or Grouping by a Label - in the SQLAlchemy 1.4 / 2.0 Tutorial
sqlalchemy.sql.expression.Select.
outerjoin(target, onclause=None, full=False)¶Create a left outer join.
Parameters are the same as that of Select.join()
.
Changed in version 1.4: Select.outerjoin()
now
creates a Join
object between a
FromClause
source that is within the FROM clause of
the existing SELECT, and a given target FromClause
,
and then adds this Join
to the FROM clause of the
newly generated SELECT statement. This is completely reworked
from the behavior in 1.3, which would instead create a subquery of
the entire
Select
and then join that subquery to the
target.
This is a backwards incompatible change as the previous behavior
was mostly useless, producing an unnamed subquery rejected by
most databases in any case. The new behavior is modeled after
that of the very successful Query.join()
method in the
ORM, in order to support the functionality of Query
being available by using a Select
object with an
Session
.
See the notes for this change at select().join() and outerjoin() add JOIN criteria to the current query, rather than creating a subquery.
See also
Explicit FROM clauses and JOINs - in the SQLAlchemy 1.4 / 2.0 Tutorial
Joins - in the ORM Querying Guide
sqlalchemy.sql.expression.Select.
outerjoin_from(from_, target, onclause=None, full=False)¶Create a SQL LEFT OUTER JOIN against this Select
object’s criterion
and apply generatively, returning the newly resulting
Select
.
Usage is the same as that of Select.join_from()
.
sqlalchemy.sql.expression.Select.
prefix_with(*expr, **kw)¶inherited from the HasPrefixes.prefix_with()
method of HasPrefixes
Add one or more expressions following the statement keyword, i.e. SELECT, INSERT, UPDATE, or DELETE. Generative.
This is used to support backend-specific prefix keywords such as those provided by MySQL.
E.g.:
stmt = table.insert().prefix_with("LOW_PRIORITY", dialect="mysql")
# MySQL 5.7 optimizer hints
stmt = select(table).prefix_with(
"/*+ BKA(t1) */", dialect="mysql")
Multiple prefixes can be specified by multiple calls
to HasPrefixes.prefix_with()
.
*expr¶ – textual or ClauseElement
construct which
will be rendered following the INSERT, UPDATE, or DELETE
keyword.
**kw¶ – A single keyword ‘dialect’ is accepted. This is an optional string dialect name which will limit rendering of this prefix to only that dialect.
sqlalchemy.sql.expression.Select.
reduce_columns(only_synonyms=True)¶Return a new select()
construct with redundantly
named, equivalently-valued columns removed from the columns clause.
“Redundant” here means two columns where one refers to the
other either based on foreign key, or via a simple equality
comparison in the WHERE clause of the statement. The primary purpose
of this method is to automatically construct a select statement
with all uniquely-named columns, without the need to use
table-qualified labels as
Select.set_label_style()
does.
When columns are omitted based on foreign key, the referred-to column is the one that’s kept. When columns are omitted based on WHERE equivalence, the first column in the columns clause is the one that’s kept.
only_synonyms¶ – when True, limit the removal of columns to those which have the same name as the equivalent. Otherwise, all columns that are equivalent to another are removed.
sqlalchemy.sql.expression.Select.
replace_selectable(old, alias)¶inherited from the Selectable.replace_selectable()
method of Selectable
Replace all occurrences of FromClause
‘old’ with the given Alias
object, returning a copy of this FromClause
.
Deprecated since version 1.4: The Selectable.replace_selectable()
method is deprecated, and will be removed in a future release. Similar functionality is available via the sqlalchemy.sql.visitors module.
sqlalchemy.sql.expression.Select.
scalar(*multiparams, **params)¶inherited from the Executable.scalar()
method of Executable
Compile and execute this Executable
, returning the
result’s scalar representation.
Deprecated since version 1.4: The Executable.scalar()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Scalar execution in SQLAlchemy 2.0 is performed by the Connection.scalar()
method of Connection
, or in the ORM by the Session.scalar()
method of Session
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.Select.
scalar_subquery()¶inherited from the SelectBase.scalar_subquery()
method of SelectBase
Return a ‘scalar’ representation of this selectable, which can be used as a column expression.
The returned object is an instance of ScalarSelect
.
Typically, a select statement which has only one column in its columns clause is eligible to be used as a scalar expression. The scalar subquery can then be used in the WHERE clause or columns clause of an enclosing SELECT.
Note that the scalar subquery differentiates from the FROM-level
subquery that can be produced using the
SelectBase.subquery()
method.
See also
Scalar and Correlated Subqueries - in the 2.0 tutorial
Scalar Selects - in the 1.x tutorial
sqlalchemy.sql.expression.Select.
select(*arg, **kw)¶inherited from the SelectBase.select()
method of SelectBase
Deprecated since version 1.4: The SelectBase.select()
method is deprecated and will be removed in a future release; this method implicitly creates a subquery that should be explicit. Please call SelectBase.subquery()
first in order to create a subquery, which then can be selected.
sqlalchemy.sql.expression.Select.
select_from(*froms)¶Return a new select()
construct with the
given FROM expression(s)
merged into its list of FROM objects.
E.g.:
table1 = table('t1', column('a'))
table2 = table('t2', column('b'))
s = select(table1.c.a).\
select_from(
table1.join(table2, table1.c.a==table2.c.b)
)
The “from” list is a unique set on the identity of each element,
so adding an already present Table
or other selectable
will have no effect. Passing a Join
that refers
to an already present Table
or other selectable will have
the effect of concealing the presence of that selectable as
an individual element in the rendered FROM list, instead
rendering it into a JOIN clause.
While the typical purpose of Select.select_from()
is to
replace the default, derived FROM clause with a join, it can
also be called with individual table elements, multiple times
if desired, in the case that the FROM clause cannot be fully
derived from the columns clause:
select(func.count('*')).select_from(table1)
sqlalchemy.sql.expression.Select.
selected_columns¶A ColumnCollection
representing the columns that
this SELECT statement or similar construct returns in its result set,
not including TextClause
constructs.
This collection differs from the FromClause.columns
collection of a FromClause
in that the columns
within this collection cannot be directly nested inside another SELECT
statement; a subquery must be applied first which provides for the
necessary parenthesization required by SQL.
For a select()
construct, the collection here is
exactly what would be rendered inside the “SELECT” statement, and the
ColumnElement
objects are directly present as they
were given, e.g.:
col1 = column('q', Integer)
col2 = column('p', Integer)
stmt = select(col1, col2)
Above, stmt.selected_columns
would be a collection that contains
the col1
and col2
objects directly. For a statement that is
against a Table
or other
FromClause
, the collection will use the
ColumnElement
objects that are in the
FromClause.c
collection of the from element.
Note
The Select.selected_columns
collection does not
include expressions established in the columns clause using the
text()
construct; these are silently omitted from the
collection. To use plain textual column expressions inside of a
Select
construct, use the literal_column()
construct.
New in version 1.4.
sqlalchemy.sql.expression.Select.
self_group(against=None)¶Return a ‘grouping’ construct as per the
ClauseElement
specification.
This produces an element that can be embedded in an expression. Note that this method is called automatically as needed when constructing expressions and should not require explicit use.
sqlalchemy.sql.expression.Select.
set_label_style(style)¶inherited from the GenerativeSelect.set_label_style()
method of GenerativeSelect
Return a new selectable with the specified label style.
There are three “label styles” available,
LABEL_STYLE_DISAMBIGUATE_ONLY
,
LABEL_STYLE_TABLENAME_PLUS_COL
, and
LABEL_STYLE_NONE
. The default style is
LABEL_STYLE_TABLENAME_PLUS_COL
.
In modern SQLAlchemy, there is not generally a need to change the
labeling style, as per-expression labels are more effectively used by
making use of the ColumnElement.label()
method. In past
versions, LABEL_STYLE_TABLENAME_PLUS_COL
was used to
disambiguate same-named columns from different tables, aliases, or
subqueries; the newer LABEL_STYLE_DISAMBIGUATE_ONLY
now
applies labels only to names that conflict with an existing name so
that the impact of this labeling is minimal.
The rationale for disambiguation is mostly so that all column
expressions are available from a given FromClause.c
collection when a subquery is created.
New in version 1.4: - the
GenerativeSelect.set_label_style()
method replaces the
previous combination of .apply_labels()
, .with_labels()
and
use_labels=True
methods and/or parameters.
sqlalchemy.sql.expression.Select.
slice(start, stop)¶inherited from the GenerativeSelect.slice()
method of GenerativeSelect
Apply LIMIT / OFFSET to this statement based on a slice.
The start and stop indices behave like the argument to Python’s
built-in range()
function. This method provides an
alternative to using LIMIT
/OFFSET
to get a slice of the
query.
For example,
stmt = select(User).order_by(User).id.slice(1, 3)
renders as
SELECT users.id AS users_id,
users.name AS users_name
FROM users ORDER BY users.id
LIMIT ? OFFSET ?
(2, 1)
Note
The GenerativeSelect.slice()
method will replace
any clause applied with GenerativeSelect.fetch()
.
New in version 1.4: Added the GenerativeSelect.slice()
method generalized from the ORM.
sqlalchemy.sql.expression.Select.
subquery(name=None)¶inherited from the SelectBase.subquery()
method of SelectBase
Return a subquery of this SelectBase
.
A subquery is from a SQL perspective a parenthesized, named construct that can be placed in the FROM clause of another SELECT statement.
Given a SELECT statement such as:
stmt = select(table.c.id, table.c.name)
The above statement might look like:
SELECT table.id, table.name FROM table
The subquery form by itself renders the same way, however when embedded into the FROM clause of another SELECT statement, it becomes a named sub-element:
subq = stmt.subquery()
new_stmt = select(subq)
The above renders as:
SELECT anon_1.id, anon_1.name
FROM (SELECT table.id, table.name FROM table) AS anon_1
Historically, SelectBase.subquery()
is equivalent to calling
the FromClause.alias()
method on a FROM object; however,
as a SelectBase
object is not directly FROM object,
the SelectBase.subquery()
method provides clearer semantics.
New in version 1.4.
sqlalchemy.sql.expression.Select.
suffix_with(*expr, **kw)¶inherited from the HasSuffixes.suffix_with()
method of HasSuffixes
Add one or more expressions following the statement as a whole.
This is used to support backend-specific suffix keywords on certain constructs.
E.g.:
stmt = select(col1, col2).cte().suffix_with(
"cycle empno set y_cycle to 1 default 0", dialect="oracle")
Multiple suffixes can be specified by multiple calls
to HasSuffixes.suffix_with()
.
*expr¶ – textual or ClauseElement
construct which
will be rendered following the target clause.
**kw¶ – A single keyword ‘dialect’ is accepted. This is an optional string dialect name which will limit rendering of this suffix to only that dialect.
sqlalchemy.sql.expression.Select.
union(other, **kwargs)¶Return a SQL UNION
of this select() construct against
the given selectable.
sqlalchemy.sql.expression.Select.
union_all(other, **kwargs)¶Return a SQL UNION ALL
of this select() construct against
the given selectable.
sqlalchemy.sql.expression.Select.
where(*whereclause)¶Return a new select()
construct with
the given expression added to
its WHERE clause, joined to the existing clause via AND, if any.
sqlalchemy.sql.expression.Select.
whereclause¶Return the completed WHERE clause for this
Select
statement.
This assembles the current collection of WHERE criteria
into a single BooleanClauseList
construct.
New in version 1.4.
sqlalchemy.sql.expression.Select.
with_for_update(nowait=False, read=False, of=None, skip_locked=False, key_share=False)¶inherited from the GenerativeSelect.with_for_update()
method of GenerativeSelect
Specify a FOR UPDATE
clause for this
GenerativeSelect
.
E.g.:
stmt = select(table).with_for_update(nowait=True)
On a database like PostgreSQL or Oracle, the above would render a statement like:
SELECT table.a, table.b FROM table FOR UPDATE NOWAIT
on other backends, the nowait
option is ignored and instead
would produce:
SELECT table.a, table.b FROM table FOR UPDATE
When called with no arguments, the statement will render with
the suffix FOR UPDATE
. Additional arguments can then be
provided which allow for common database-specific
variants.
nowait¶ – boolean; will render FOR UPDATE NOWAIT
on Oracle
and PostgreSQL dialects.
read¶ – boolean; will render LOCK IN SHARE MODE
on MySQL,
FOR SHARE
on PostgreSQL. On PostgreSQL, when combined with
nowait
, will render FOR SHARE NOWAIT
.
of¶ – SQL expression or list of SQL expression elements
(typically Column
objects or a compatible expression) which
will render into a FOR UPDATE OF
clause; supported by PostgreSQL
and Oracle. May render as a table or as a column depending on
backend.
skip_locked¶ – boolean, will render FOR UPDATE SKIP LOCKED
on Oracle and PostgreSQL dialects or FOR SHARE SKIP LOCKED
if
read=True
is also specified.
key_share¶ – boolean, will render FOR NO KEY UPDATE
,
or if combined with read=True
will render FOR KEY SHARE
,
on the PostgreSQL dialect.
sqlalchemy.sql.expression.Select.
with_hint(selectable, text, dialect_name='*')¶inherited from the HasHints.with_hint()
method of HasHints
Add an indexing or other executional context hint for the given
selectable to this Select
or other selectable
object.
The text of the hint is rendered in the appropriate
location for the database backend in use, relative
to the given Table
or Alias
passed as the
selectable
argument. The dialect implementation
typically uses Python string substitution syntax
with the token %(name)s
to render the name of
the table or alias. E.g. when using Oracle, the
following:
select(mytable).\
with_hint(mytable, "index(%(name)s ix_mytable)")
Would render SQL as:
select /*+ index(mytable ix_mytable) */ ... from mytable
The dialect_name
option will limit the rendering of a particular
hint to a particular backend. Such as, to add hints for both Oracle
and Sybase simultaneously:
select(mytable).\
with_hint(mytable, "index(%(name)s ix_mytable)", 'oracle').\
with_hint(mytable, "WITH INDEX ix_mytable", 'sybase')
See also
sqlalchemy.sql.expression.Select.
with_only_columns(*columns)¶Return a new select()
construct with its columns
clause replaced with the given columns.
This method is exactly equivalent to as if the original
select()
had been called with the given columns
clause. I.e. a statement:
s = select(table1.c.a, table1.c.b)
s = s.with_only_columns(table1.c.b)
should be exactly equivalent to:
s = select(table1.c.b)
Note that this will also dynamically alter the FROM clause of the
statement if it is not explicitly stated. To maintain the FROM
clause, ensure the Select.select_from()
method is
used appropriately:
s = select(table1.c.a, table2.c.b)
s = s.select_from(table2.c.b).with_only_columns(table1.c.a)
*columns¶ –
column expressions to be used.
Changed in version 1.4: the Select.with_only_columns()
method accepts the list of column expressions positionally;
passing the expressions as a list is deprecated.
sqlalchemy.sql.expression.Select.
with_statement_hint(text, dialect_name='*')¶inherited from the HasHints.with_statement_hint()
method of HasHints
Add a statement hint to this Select
or
other selectable object.
This method is similar to Select.with_hint()
except that
it does not require an individual table, and instead applies to the
statement as a whole.
Hints here are specific to the backend database and may include directives such as isolation levels, file directives, fetch directives, etc.
New in version 1.0.0.
See also
Select.prefix_with()
- generic SELECT prefixing
which also can suit some database-specific HINT syntaxes such as
MySQL optimizer hints
Mark a class as being selectable.
Class signature
class sqlalchemy.sql.expression.Selectable
(sqlalchemy.sql.expression.ReturnsRows
)
sqlalchemy.sql.expression.Selectable.
corresponding_column(column, require_embedded=False)¶Given a ColumnElement
, return the exported
ColumnElement
object from the
Selectable.exported_columns
collection of this Selectable
which corresponds to that
original ColumnElement
via a common ancestor
column.
column¶ – the target ColumnElement
to be matched.
require_embedded¶ – only return corresponding columns for
the given ColumnElement
, if the given
ColumnElement
is actually present within a sub-element
of this Selectable
.
Normally the column will match if
it merely shares a common ancestor with one of the exported
columns of this Selectable
.
See also
Selectable.exported_columns
- the
ColumnCollection
that is used for the operation.
ColumnCollection.corresponding_column()
- implementation
method.
sqlalchemy.sql.expression.Selectable.
exported_columns¶inherited from the ReturnsRows.exported_columns
attribute of ReturnsRows
A ColumnCollection
that represents the “exported”
columns of this ReturnsRows
.
The “exported” columns represent the collection of
ColumnElement
expressions that are rendered by this SQL
construct. There are primary varieties which are the
“FROM clause columns” of a FROM clause, such as a table, join,
or subquery, the “SELECTed columns”, which are the columns in
the “columns clause” of a SELECT statement, and the RETURNING
columns in a DML statement..
New in version 1.4.
sqlalchemy.sql.expression.Selectable.
lateral(name=None)¶Return a LATERAL alias of this Selectable
.
The return value is the Lateral
construct also
provided by the top-level lateral()
function.
New in version 1.1.
See also
LATERAL correlation - overview of usage.
sqlalchemy.sql.expression.Selectable.
replace_selectable(old, alias)¶Replace all occurrences of FromClause
‘old’ with the given Alias
object, returning a copy of this FromClause
.
Deprecated since version 1.4: The Selectable.replace_selectable()
method is deprecated, and will be removed in a future release. Similar functionality is available via the sqlalchemy.sql.visitors module.
Base class for SELECT statements.
This includes Select
,
CompoundSelect
and
TextualSelect
.
Class signature
class sqlalchemy.sql.expression.SelectBase
(sqlalchemy.sql.roles.SelectStatementRole
, sqlalchemy.sql.roles.DMLSelectRole
, sqlalchemy.sql.roles.CompoundElementRole
, sqlalchemy.sql.roles.InElementRole
, sqlalchemy.sql.expression.HasCTE
, sqlalchemy.sql.expression.Executable
, sqlalchemy.sql.annotation.SupportsCloneAnnotations
, sqlalchemy.sql.expression.Selectable
)
sqlalchemy.sql.expression.SelectBase.
alias(name=None, flat=False)¶Return a named subquery against this
SelectBase
.
For a SelectBase
(as opposed to a
FromClause
),
this returns a Subquery
object which behaves mostly the
same as the Alias
object that is used with a
FromClause
.
Changed in version 1.4: The SelectBase.alias()
method is now
a synonym for the SelectBase.subquery()
method.
sqlalchemy.sql.expression.SelectBase.
as_scalar()¶Deprecated since version 1.4: The SelectBase.as_scalar()
method is deprecated and will be removed in a future release. Please refer to SelectBase.scalar_subquery()
.
sqlalchemy.sql.expression.SelectBase.
bind¶inherited from the Executable.bind
attribute of Executable
Returns the Engine
or Connection
to
which this Executable
is bound, or None if none found.
Deprecated since version 1.4: The Executable.bind
attribute is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Bound metadata is being removed as of SQLAlchemy 2.0. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
This is a traversal which checks locally, then checks among the “from” clauses of associated objects until a bound engine or connection is found.
sqlalchemy.sql.expression.SelectBase.
c¶Deprecated since version 1.4: The SelectBase.c
and SelectBase.columns
attributes are deprecated and will be removed in a future release; these attributes implicitly create a subquery that should be explicit. Please call SelectBase.subquery()
first in order to create a subquery, which then contains this attribute. To access the columns that this SELECT object SELECTs from, use the SelectBase.selected_columns
attribute.
sqlalchemy.sql.expression.SelectBase.
corresponding_column(column, require_embedded=False)¶inherited from the Selectable.corresponding_column()
method of Selectable
Given a ColumnElement
, return the exported
ColumnElement
object from the
Selectable.exported_columns
collection of this Selectable
which corresponds to that
original ColumnElement
via a common ancestor
column.
column¶ – the target ColumnElement
to be matched.
require_embedded¶ – only return corresponding columns for
the given ColumnElement
, if the given
ColumnElement
is actually present within a sub-element
of this Selectable
.
Normally the column will match if
it merely shares a common ancestor with one of the exported
columns of this Selectable
.
See also
Selectable.exported_columns
- the
ColumnCollection
that is used for the operation.
ColumnCollection.corresponding_column()
- implementation
method.
sqlalchemy.sql.expression.SelectBase.
cte(name=None, recursive=False)¶inherited from the HasCTE.cte()
method of HasCTE
Return a new CTE
,
or Common Table Expression instance.
Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
CTEs can also be applied to DML constructs UPDATE, INSERT and DELETE on some databases, both as a source of CTE rows when combined with RETURNING, as well as a consumer of CTE rows.
Changed in version 1.1: Added support for UPDATE/INSERT/DELETE as CTE, CTEs added to UPDATE/INSERT/DELETE.
SQLAlchemy detects CTE
objects, which are treated
similarly to Alias
objects, as special elements
to be delivered to the FROM clause of the statement as well
as to a WITH clause at the top of the statement.
For special prefixes such as PostgreSQL “MATERIALIZED” and
“NOT MATERIALIZED”, the CTE.prefix_with()
method may be
used to establish these.
Changed in version 1.3.13: Added support for prefixes. In particular - MATERIALIZED and NOT MATERIALIZED.
name¶ – name given to the common table expression. Like
FromClause.alias()
, the name can be left as
None
in which case an anonymous symbol will be used at query
compile time.
recursive¶ – if True
, will render WITH RECURSIVE
.
A recursive common table expression is intended to be used in
conjunction with UNION ALL in order to derive rows
from those already selected.
The following examples include two from PostgreSQL’s documentation at http://www.postgresql.org/docs/current/static/queries-with.html, as well as additional examples.
Example 1, non recursive:
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
orders = Table('orders', metadata,
Column('region', String),
Column('amount', Integer),
Column('product', String),
Column('quantity', Integer)
)
regional_sales = select(
orders.c.region,
func.sum(orders.c.amount).label('total_sales')
).group_by(orders.c.region).cte("regional_sales")
top_regions = select(regional_sales.c.region).\
where(
regional_sales.c.total_sales >
select(
func.sum(regional_sales.c.total_sales) / 10
)
).cte("top_regions")
statement = select(
orders.c.region,
orders.c.product,
func.sum(orders.c.quantity).label("product_units"),
func.sum(orders.c.amount).label("product_sales")
).where(orders.c.region.in_(
select(top_regions.c.region)
)).group_by(orders.c.region, orders.c.product)
result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
parts = Table('parts', metadata,
Column('part', String),
Column('sub_part', String),
Column('quantity', Integer),
)
included_parts = select(\
parts.c.sub_part, parts.c.part, parts.c.quantity\
).\
where(parts.c.part=='our part').\
cte(recursive=True)
incl_alias = included_parts.alias()
parts_alias = parts.alias()
included_parts = included_parts.union_all(
select(
parts_alias.c.sub_part,
parts_alias.c.part,
parts_alias.c.quantity
).\
where(parts_alias.c.part==incl_alias.c.sub_part)
)
statement = select(
included_parts.c.sub_part,
func.sum(included_parts.c.quantity).
label('total_quantity')
).\
group_by(included_parts.c.sub_part)
result = conn.execute(statement).fetchall()
Example 3, an upsert using UPDATE and INSERT with CTEs:
from datetime import date
from sqlalchemy import (MetaData, Table, Column, Integer,
Date, select, literal, and_, exists)
metadata = MetaData()
visitors = Table('visitors', metadata,
Column('product_id', Integer, primary_key=True),
Column('date', Date, primary_key=True),
Column('count', Integer),
)
# add 5 visitors for the product_id == 1
product_id = 1
day = date.today()
count = 5
update_cte = (
visitors.update()
.where(and_(visitors.c.product_id == product_id,
visitors.c.date == day))
.values(count=visitors.c.count + count)
.returning(literal(1))
.cte('update_cte')
)
upsert = visitors.insert().from_select(
[visitors.c.product_id, visitors.c.date, visitors.c.count],
select(literal(product_id), literal(day), literal(count))
.where(~exists(update_cte.select()))
)
connection.execute(upsert)
See also
Query.cte()
- ORM version of
HasCTE.cte()
.
sqlalchemy.sql.expression.SelectBase.
execute(*multiparams, **params)¶inherited from the Executable.execute()
method of Executable
Compile and execute this Executable
.
Deprecated since version 1.4: The Executable.execute()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. All statement execution in SQLAlchemy 2.0 is performed by the Connection.execute()
method of Connection
, or in the ORM by the Session.execute()
method of Session
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.SelectBase.
execution_options(**kw)¶inherited from the Executable.execution_options()
method of Executable
Set non-SQL options for the statement which take effect during execution.
Execution options can be set on a per-statement or
per Connection
basis. Additionally, the
Engine
and ORM Query
objects provide
access to execution options which they in turn configure upon
connections.
The execution_options()
method is generative. A new
instance of this statement is returned that contains the options:
statement = select(table.c.x, table.c.y)
statement = statement.execution_options(autocommit=True)
Note that only a subset of possible execution options can be applied
to a statement - these include “autocommit” and “stream_results”,
but not “isolation_level” or “compiled_cache”.
See Connection.execution_options()
for a full list of
possible options.
sqlalchemy.sql.expression.SelectBase.
exists()¶Return an Exists
representation of this selectable,
which can be used as a column expression.
The returned object is an instance of Exists
.
New in version 1.4.
sqlalchemy.sql.expression.SelectBase.
exported_columns¶A ColumnCollection
that represents the “exported”
columns of this Selectable
, not including
TextClause
constructs.
The “exported” columns for a SelectBase
object are synonymous
with the SelectBase.selected_columns
collection.
New in version 1.4.
sqlalchemy.sql.expression.SelectBase.
get_execution_options()¶inherited from the Executable.get_execution_options()
method of Executable
Get the non-SQL options which will take effect during execution.
New in version 1.3.
See also
sqlalchemy.sql.expression.SelectBase.
label(name)¶Return a ‘scalar’ representation of this selectable, embedded as a subquery with a label.
See also
sqlalchemy.sql.expression.SelectBase.
lateral(name=None)¶Return a LATERAL alias of this Selectable
.
The return value is the Lateral
construct also
provided by the top-level lateral()
function.
New in version 1.1.
See also
LATERAL correlation - overview of usage.
sqlalchemy.sql.expression.SelectBase.
options(*options)¶inherited from the Executable.options()
method of Executable
Apply options to this statement.
In the general sense, options are any kind of Python object that can be interpreted by the SQL compiler for the statement. These options can be consumed by specific dialects or specific kinds of compilers.
The most commonly known kind of option are the ORM level options that apply “eager load” and other loading behaviors to an ORM query. However, options can theoretically be used for many other purposes.
For background on specific kinds of options for specific kinds of statements, refer to the documentation for those option objects.
Changed in version 1.4: - added Generative.options()
to
Core statement objects towards the goal of allowing unified
Core / ORM querying capabilities.
See also
Deferred Column Loader Query Options - refers to options specific to the usage of ORM queries
Relationship Loading with Loader Options - refers to options specific to the usage of ORM queries
sqlalchemy.sql.expression.SelectBase.
replace_selectable(old, alias)¶inherited from the Selectable.replace_selectable()
method of Selectable
Replace all occurrences of FromClause
‘old’ with the given Alias
object, returning a copy of this FromClause
.
Deprecated since version 1.4: The Selectable.replace_selectable()
method is deprecated, and will be removed in a future release. Similar functionality is available via the sqlalchemy.sql.visitors module.
sqlalchemy.sql.expression.SelectBase.
scalar(*multiparams, **params)¶inherited from the Executable.scalar()
method of Executable
Compile and execute this Executable
, returning the
result’s scalar representation.
Deprecated since version 1.4: The Executable.scalar()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Scalar execution in SQLAlchemy 2.0 is performed by the Connection.scalar()
method of Connection
, or in the ORM by the Session.scalar()
method of Session
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.SelectBase.
scalar_subquery()¶Return a ‘scalar’ representation of this selectable, which can be used as a column expression.
The returned object is an instance of ScalarSelect
.
Typically, a select statement which has only one column in its columns clause is eligible to be used as a scalar expression. The scalar subquery can then be used in the WHERE clause or columns clause of an enclosing SELECT.
Note that the scalar subquery differentiates from the FROM-level
subquery that can be produced using the
SelectBase.subquery()
method.
See also
Scalar and Correlated Subqueries - in the 2.0 tutorial
Scalar Selects - in the 1.x tutorial
sqlalchemy.sql.expression.SelectBase.
select(*arg, **kw)¶Deprecated since version 1.4: The SelectBase.select()
method is deprecated and will be removed in a future release; this method implicitly creates a subquery that should be explicit. Please call SelectBase.subquery()
first in order to create a subquery, which then can be selected.
sqlalchemy.sql.expression.SelectBase.
selected_columns¶A ColumnCollection
representing the columns that
this SELECT statement or similar construct returns in its result set.
This collection differs from the FromClause.columns
collection of a FromClause
in that the columns
within this collection cannot be directly nested inside another SELECT
statement; a subquery must be applied first which provides for the
necessary parenthesization required by SQL.
Note
The SelectBase.selected_columns
collection does not
include expressions established in the columns clause using the
text()
construct; these are silently omitted from the
collection. To use plain textual column expressions inside of a
Select
construct, use the literal_column()
construct.
See also
New in version 1.4.
sqlalchemy.sql.expression.SelectBase.
subquery(name=None)¶Return a subquery of this SelectBase
.
A subquery is from a SQL perspective a parenthesized, named construct that can be placed in the FROM clause of another SELECT statement.
Given a SELECT statement such as:
stmt = select(table.c.id, table.c.name)
The above statement might look like:
SELECT table.id, table.name FROM table
The subquery form by itself renders the same way, however when embedded into the FROM clause of another SELECT statement, it becomes a named sub-element:
subq = stmt.subquery()
new_stmt = select(subq)
The above renders as:
SELECT anon_1.id, anon_1.name
FROM (SELECT table.id, table.name FROM table) AS anon_1
Historically, SelectBase.subquery()
is equivalent to calling
the FromClause.alias()
method on a FROM object; however,
as a SelectBase
object is not directly FROM object,
the SelectBase.subquery()
method provides clearer semantics.
New in version 1.4.
Represent a subquery of a SELECT.
A Subquery
is created by invoking the
SelectBase.subquery()
method, or for convenience the
SelectBase.alias()
method, on any
SelectBase
subclass
which includes Select
,
CompoundSelect
, and
TextualSelect
. As rendered in a FROM clause,
it represents the
body of the SELECT statement inside of parenthesis, followed by the usual
“AS <somename>” that defines all “alias” objects.
The Subquery
object is very similar to the
Alias
object and can be used in an equivalent way. The difference between
Alias
and Subquery
is that
Alias
always
contains a FromClause
object whereas
Subquery
always contains a SelectBase
object.
New in version 1.4: The Subquery
class was added which now
serves the purpose of providing an aliased version of a SELECT
statement.
Class signature
class sqlalchemy.sql.expression.Subquery
(sqlalchemy.sql.expression.AliasedReturnsRows
)
sqlalchemy.sql.expression.Subquery.
as_scalar()¶Deprecated since version 1.4: The Subquery.as_scalar()
method, which was previously Alias.as_scalar()
prior to version 1.4, is deprecated and will be removed in a future release; Please use the Select.scalar_subquery()
method of the select()
construct before constructing a subquery object, or with the ORM use the Query.scalar_subquery()
method.
Represents a minimal “table” construct.
This is a lightweight table object that has only a name, a
collection of columns, which are typically produced
by the column()
function, and a schema:
from sqlalchemy import table, column
user = table("user",
column("id"),
column("name"),
column("description"),
)
The TableClause
construct serves as the base for
the more commonly used Table
object, providing
the usual set of FromClause
services including
the .c.
collection and statement generation methods.
It does not provide all the additional schema-level services
of Table
, including constraints, references to other
tables, or support for MetaData
-level services.
It’s useful
on its own as an ad-hoc construct used to generate quick SQL
statements when a more fully fledged Table
is not on hand.
Class signature
class sqlalchemy.sql.expression.TableClause
(sqlalchemy.sql.roles.DMLTableRole
, sqlalchemy.sql.expression.Immutable
, sqlalchemy.sql.expression.FromClause
)
sqlalchemy.sql.expression.TableClause.
__init__(name, *columns, **kw)¶Construct a new TableClause
object.
This constructor is mirrored as a public API function; see sqlalchemy.sql.expression.table()
for a full usage and argument description.
sqlalchemy.sql.expression.TableClause.
alias(name=None, flat=False)¶inherited from the FromClause.alias()
method of FromClause
Return an alias of this FromClause
.
E.g.:
a2 = some_table.alias('a2')
The above code creates an Alias
object which can be used
as a FROM clause in any SELECT statement.
sqlalchemy.sql.expression.TableClause.
c¶inherited from the FromClause.c
attribute of FromClause
A named-based collection of ColumnElement
objects maintained by this FromClause
.
The FromClause.c
attribute is an alias for the
FromClause.columns
atttribute.
sqlalchemy.sql.expression.TableClause.
columns¶inherited from the FromClause.columns
attribute of FromClause
A named-based collection of ColumnElement
objects maintained by this FromClause
.
The columns
, or c
collection, is the gateway
to the construction of SQL expressions using table-bound or
other selectable-bound columns:
select(mytable).where(mytable.c.somecolumn == 5)
a ColumnCollection
object.
sqlalchemy.sql.expression.TableClause.
compare(other, **kw)¶inherited from the ClauseElement.compare()
method of ClauseElement
Compare this ClauseElement
to
the given ClauseElement
.
Subclasses should override the default behavior, which is a straight identity comparison.
**kw are arguments consumed by subclass compare()
methods and
may be used to modify the criteria for comparison
(see ColumnElement
).
sqlalchemy.sql.expression.TableClause.
compile(bind=None, dialect=None, **kw)¶inherited from the ClauseElement.compile()
method of ClauseElement
Compile this SQL expression.
The return value is a Compiled
object.
Calling str()
or unicode()
on the returned value will yield a
string representation of the result. The
Compiled
object also can return a
dictionary of bind parameter names and values
using the params
accessor.
bind¶ – An Engine
or Connection
from which a
Compiled
will be acquired. This argument takes precedence over
this ClauseElement
’s bound engine, if any.
column_keys¶ – Used for INSERT and UPDATE statements, a list of
column names which should be present in the VALUES clause of the
compiled statement. If None
, all columns from the target table
object are rendered.
dialect¶ – A Dialect
instance from which a Compiled
will be acquired. This argument takes precedence over the bind
argument as well as this ClauseElement
‘s bound engine,
if any.
compile_kwargs¶ –
optional dictionary of additional parameters
that will be passed through to the compiler within all “visit”
methods. This allows any custom flag to be passed through to
a custom compilation construct, for example. It is also used
for the case of passing the literal_binds
flag through:
from sqlalchemy.sql import table, column, select
t = table('t', column('x'))
s = select(t).where(t.c.x == 5)
print(s.compile(compile_kwargs={"literal_binds": True}))
New in version 0.9.0.
sqlalchemy.sql.expression.TableClause.
corresponding_column(column, require_embedded=False)¶inherited from the Selectable.corresponding_column()
method of Selectable
Given a ColumnElement
, return the exported
ColumnElement
object from the
Selectable.exported_columns
collection of this Selectable
which corresponds to that
original ColumnElement
via a common ancestor
column.
column¶ – the target ColumnElement
to be matched.
require_embedded¶ – only return corresponding columns for
the given ColumnElement
, if the given
ColumnElement
is actually present within a sub-element
of this Selectable
.
Normally the column will match if
it merely shares a common ancestor with one of the exported
columns of this Selectable
.
See also
Selectable.exported_columns
- the
ColumnCollection
that is used for the operation.
ColumnCollection.corresponding_column()
- implementation
method.
sqlalchemy.sql.expression.TableClause.
delete(whereclause=None, **kwargs)¶Generate a delete()
construct against this
TableClause
.
E.g.:
table.delete().where(table.c.id==7)
See delete()
for argument and usage information.
sqlalchemy.sql.expression.TableClause.
entity_namespace¶inherited from the FromClause.entity_namespace
attribute of FromClause
Return a namespace used for name-based access in SQL expressions.
This is the namespace that is used to resolve “filter_by()” type expressions, such as:
stmt.filter_by(address='some address')
It defaults to the .c
collection, however internally it can
be overridden using the “entity_namespace” annotation to deliver
alternative results.
sqlalchemy.sql.expression.TableClause.
exported_columns¶inherited from the FromClause.exported_columns
attribute of FromClause
A ColumnCollection
that represents the “exported”
columns of this Selectable
.
The “exported” columns for a FromClause
object are synonymous
with the FromClause.columns
collection.
New in version 1.4.
sqlalchemy.sql.expression.TableClause.
foreign_keys¶inherited from the FromClause.foreign_keys
attribute of FromClause
Return the collection of ForeignKey
marker objects
which this FromClause references.
Each ForeignKey
is a member of a
Table
-wide
ForeignKeyConstraint
.
See also
sqlalchemy.sql.expression.TableClause.
get_children(omit_attrs=(), **kw)¶inherited from the ClauseElement.get_children()
method of ClauseElement
Return immediate child Traversible
elements of this Traversible
.
This is used for visit traversal.
**kw may contain flags that change the collection that is returned, for example to return a subset of items in order to cut down on larger traversals, or to return child items from a different context (such as schema-level collections instead of clause-level).
sqlalchemy.sql.expression.TableClause.
implicit_returning = False¶TableClause
doesn’t support having a primary key or column
-level defaults, so implicit returning doesn’t apply.
sqlalchemy.sql.expression.TableClause.
insert(values=None, inline=False, **kwargs)¶Generate an insert()
construct against this
TableClause
.
E.g.:
table.insert().values(name='foo')
See insert()
for argument and usage information.
sqlalchemy.sql.expression.TableClause.
is_derived_from(fromclause)¶inherited from the FromClause.is_derived_from()
method of FromClause
Return True
if this FromClause
is
‘derived’ from the given FromClause
.
An example would be an Alias of a Table is derived from that Table.
sqlalchemy.sql.expression.TableClause.
join(right, onclause=None, isouter=False, full=False)¶inherited from the FromClause.join()
method of FromClause
Return a Join
from this
FromClause
to another FromClause
.
E.g.:
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select(user_table).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
right¶ – the right side of the join; this is any
FromClause
object such as a
Table
object, and
may also be a selectable-compatible object such as an ORM-mapped
class.
onclause¶ – a SQL expression representing the ON clause of the
join. If left at None
, FromClause.join()
will attempt to
join the two tables based on a foreign key relationship.
isouter¶ – if True, render a LEFT OUTER JOIN, instead of JOIN.
full¶ –
if True, render a FULL OUTER JOIN, instead of LEFT OUTER
JOIN. Implies FromClause.join.isouter
.
New in version 1.1.
sqlalchemy.sql.expression.TableClause.
lateral(name=None)¶inherited from the Selectable.lateral()
method of Selectable
Return a LATERAL alias of this Selectable
.
The return value is the Lateral
construct also
provided by the top-level lateral()
function.
New in version 1.1.
See also
LATERAL correlation - overview of usage.
A read-only @property that is only evaluated once.
sqlalchemy.sql.expression.TableClause.
classmethod memoized_instancemethod(fn)¶inherited from the HasMemoized.memoized_instancemethod()
method of HasMemoized
Decorate a method memoize its return value.
sqlalchemy.sql.expression.TableClause.
outerjoin(right, onclause=None, full=False)¶inherited from the FromClause.outerjoin()
method of FromClause
Return a Join
from this
FromClause
to another FromClause
, with the “isouter” flag set to
True.
E.g.:
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to:
j = user_table.join(
address_table,
user_table.c.id == address_table.c.user_id,
isouter=True)
right¶ – the right side of the join; this is any
FromClause
object such as a
Table
object, and
may also be a selectable-compatible object such as an ORM-mapped
class.
onclause¶ – a SQL expression representing the ON clause of the
join. If left at None
, FromClause.join()
will attempt to
join the two tables based on a foreign key relationship.
full¶ –
if True, render a FULL OUTER JOIN, instead of LEFT OUTER JOIN.
New in version 1.1.
sqlalchemy.sql.expression.TableClause.
primary_key¶inherited from the FromClause.primary_key
attribute of FromClause
Return the iterable collection of Column
objects
which comprise the primary key of this _selectable.FromClause
.
For a Table
object, this collection is represented
by the PrimaryKeyConstraint
which itself is an
iterable collection of Column
objects.
sqlalchemy.sql.expression.TableClause.
replace_selectable(old, alias)¶inherited from the Selectable.replace_selectable()
method of Selectable
Replace all occurrences of FromClause
‘old’ with the given Alias
object, returning a copy of this FromClause
.
Deprecated since version 1.4: The Selectable.replace_selectable()
method is deprecated, and will be removed in a future release. Similar functionality is available via the sqlalchemy.sql.visitors module.
sqlalchemy.sql.expression.TableClause.
select(whereclause=None, **kwargs)¶inherited from the FromClause.select()
method of FromClause
Return a SELECT of this FromClause
.
e.g.:
stmt = some_table.select().where(some_table.c.id == 5)
whereclause¶ –
a WHERE clause, equivalent to calling the
Select.where()
method.
Deprecated since version 1.4: The FromClause.select().whereclause
parameter is deprecated and will be removed in version 2.0. Please make use of the Select.where()
method to add WHERE criteria to the SELECT statement.
**kwargs¶ – additional keyword arguments are passed to the
legacy constructor for Select
described at
Select.create_legacy_select()
.
See also
select()
- general purpose
method which allows for arbitrary column lists.
sqlalchemy.sql.expression.TableClause.
self_group(against: Optional[Any] = None) → ClauseElement¶inherited from the ClauseElement.self_group()
method of ClauseElement
Apply a ‘grouping’ to this ClauseElement
.
This method is overridden by subclasses to return a “grouping”
construct, i.e. parenthesis. In particular it’s used by “binary”
expressions to provide a grouping around themselves when placed into a
larger expression, as well as by select()
constructs when placed into the FROM clause of another
select()
. (Note that subqueries should be
normally created using the Select.alias()
method,
as many
platforms require nested SELECT statements to be named).
As expressions are composed together, the application of
self_group()
is automatic - end-user code should never
need to use this method directly. Note that SQLAlchemy’s
clause constructs take operator precedence into account -
so parenthesis might not be needed, for example, in
an expression like x OR (y AND z)
- AND takes precedence
over OR.
The base self_group()
method of
ClauseElement
just returns self.
sqlalchemy.sql.expression.TableClause.
table_valued()¶inherited from the FromClause.table_valued()
method of FromClause
Return a TableValuedColumn
object for this
FromClause
.
A TableValuedColumn
is a ColumnElement
that
represents a complete row in a table. Support for this construct is
backend dependent, and is supported in various forms by backends
such as PostgreSQL, Oracle and SQL Server.
E.g.:
>>> from sqlalchemy import select, column, func, table
>>> a = table("a", column("id"), column("x"), column("y"))
>>> stmt = select(func.row_to_json(a.table_valued()))
>>> print(stmt)
SELECT row_to_json(a) AS row_to_json_1
FROM a
New in version 1.4.0b2.
See also
Working with SQL Functions - in the SQLAlchemy 1.4 / 2.0 Tutorial
sqlalchemy.sql.expression.TableClause.
tablesample(sampling, name=None, seed=None)¶inherited from the FromClause.tablesample()
method of FromClause
Return a TABLESAMPLE alias of this FromClause
.
The return value is the TableSample
construct also
provided by the top-level tablesample()
function.
New in version 1.1.
See also
tablesample()
- usage guidelines and parameters
sqlalchemy.sql.expression.TableClause.
update(whereclause=None, values=None, inline=False, **kwargs)¶Generate an update()
construct against this
TableClause
.
E.g.:
table.update().where(table.c.id==7).values(name='foo')
See update()
for argument and usage information.
Represent a TABLESAMPLE clause.
This object is constructed from the tablesample()
module
level function as well as the FromClause.tablesample()
method
available on all FromClause
subclasses.
New in version 1.1.
See also
Class signature
class sqlalchemy.sql.expression.TableSample
(sqlalchemy.sql.expression.AliasedReturnsRows
)
An alias against a “table valued” SQL function.
This construct provides for a SQL function that returns columns
to be used in the FROM clause of a SELECT statement. The
object is generated using the FunctionElement.table_valued()
method, e.g.:
>>> from sqlalchemy import select, func
>>> fn = func.json_array_elements_text('["one", "two", "three"]').table_valued("value")
>>> print(select(fn.c.value))
SELECT anon_1.value
FROM json_array_elements_text(:json_array_elements_text_1) AS anon_1
New in version 1.4.0b2.
See also
Table-Valued Functions - in the SQLAlchemy 1.4 / 2.0 Tutorial
Class signature
class sqlalchemy.sql.expression.TableValuedAlias
(sqlalchemy.sql.expression.Alias
)
sqlalchemy.sql.expression.TableValuedAlias.
alias(name=None)¶Return a new alias of this TableValuedAlias
.
This creates a distinct FROM object that will be distinguished from the original one when used in a SQL statement.
sqlalchemy.sql.expression.TableValuedAlias.
column¶Return a column expression representing this
TableValuedAlias
.
This accessor is used to implement the
FunctionElement.column_valued()
method. See that
method for further details.
E.g.:
>>> print(select(func.some_func().table_valued("value").column))
SELECT anon_1 FROM some_func() AS anon_1
See also
sqlalchemy.sql.expression.TableValuedAlias.
lateral(name=None)¶Return a new TableValuedAlias
with the lateral flag set,
so that it renders as LATERAL.
See also
sqlalchemy.sql.expression.TableValuedAlias.
render_derived(name=None, with_types=False)¶Apply “render derived” to this TableValuedAlias
.
This has the effect of the individual column names listed out after the alias name in the “AS” sequence, e.g.:
>>> print(
... select(
... func.unnest(array(["one", "two", "three"])).
table_valued("x", with_ordinality="o").render_derived()
... )
... )
SELECT anon_1.x, anon_1.o
FROM unnest(ARRAY[%(param_1)s, %(param_2)s, %(param_3)s]) WITH ORDINALITY AS anon_1(x, o)
The with_types
keyword will render column types inline within
the alias expression (this syntax currently applies to the
PostgreSQL database):
>>> print(
... select(
... func.json_to_recordset(
... '[{"a":1,"b":"foo"},{"a":"2","c":"bar"}]'
... )
... .table_valued(column("a", Integer), column("b", String))
... .render_derived(with_types=True)
... )
... )
SELECT anon_1.a, anon_1.b FROM json_to_recordset(:json_to_recordset_1)
AS anon_1(a INTEGER, b VARCHAR)
name¶ – optional string name that will be applied to the alias generated. If left as None, a unique anonymizing name will be used.
with_types¶ – if True, the derived columns will include the datatype specification with each column. This is a special syntax currently known to be required by PostgreSQL for some SQL functions.
Wrap a TextClause
construct within a
SelectBase
interface.
This allows the TextClause
object to gain a
.c
collection
and other FROM-like capabilities such as
FromClause.alias()
,
SelectBase.cte()
, etc.
The TextualSelect
construct is produced via the
TextClause.columns()
method - see that method for details.
Changed in version 1.4: the TextualSelect
class was renamed
from TextAsFrom
, to more correctly suit its role as a
SELECT-oriented object and not a FROM clause.
Class signature
class sqlalchemy.sql.expression.TextualSelect
(sqlalchemy.sql.expression.SelectBase
)
sqlalchemy.sql.expression.TextualSelect.
alias(name=None, flat=False)¶inherited from the SelectBase.alias()
method of SelectBase
Return a named subquery against this
SelectBase
.
For a SelectBase
(as opposed to a
FromClause
),
this returns a Subquery
object which behaves mostly the
same as the Alias
object that is used with a
FromClause
.
Changed in version 1.4: The SelectBase.alias()
method is now
a synonym for the SelectBase.subquery()
method.
sqlalchemy.sql.expression.TextualSelect.
as_scalar()¶inherited from the SelectBase.as_scalar()
method of SelectBase
Deprecated since version 1.4: The SelectBase.as_scalar()
method is deprecated and will be removed in a future release. Please refer to SelectBase.scalar_subquery()
.
sqlalchemy.sql.expression.TextualSelect.
bind¶inherited from the Executable.bind
attribute of Executable
Returns the Engine
or Connection
to
which this Executable
is bound, or None if none found.
Deprecated since version 1.4: The Executable.bind
attribute is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Bound metadata is being removed as of SQLAlchemy 2.0. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
This is a traversal which checks locally, then checks among the “from” clauses of associated objects until a bound engine or connection is found.
sqlalchemy.sql.expression.TextualSelect.
c¶inherited from the SelectBase.c
attribute of SelectBase
Deprecated since version 1.4: The SelectBase.c
and SelectBase.columns
attributes are deprecated and will be removed in a future release; these attributes implicitly create a subquery that should be explicit. Please call SelectBase.subquery()
first in order to create a subquery, which then contains this attribute. To access the columns that this SELECT object SELECTs from, use the SelectBase.selected_columns
attribute.
sqlalchemy.sql.expression.TextualSelect.
compare(other, **kw)¶inherited from the ClauseElement.compare()
method of ClauseElement
Compare this ClauseElement
to
the given ClauseElement
.
Subclasses should override the default behavior, which is a straight identity comparison.
**kw are arguments consumed by subclass compare()
methods and
may be used to modify the criteria for comparison
(see ColumnElement
).
sqlalchemy.sql.expression.TextualSelect.
compile(bind=None, dialect=None, **kw)¶inherited from the ClauseElement.compile()
method of ClauseElement
Compile this SQL expression.
The return value is a Compiled
object.
Calling str()
or unicode()
on the returned value will yield a
string representation of the result. The
Compiled
object also can return a
dictionary of bind parameter names and values
using the params
accessor.
bind¶ – An Engine
or Connection
from which a
Compiled
will be acquired. This argument takes precedence over
this ClauseElement
’s bound engine, if any.
column_keys¶ – Used for INSERT and UPDATE statements, a list of
column names which should be present in the VALUES clause of the
compiled statement. If None
, all columns from the target table
object are rendered.
dialect¶ – A Dialect
instance from which a Compiled
will be acquired. This argument takes precedence over the bind
argument as well as this ClauseElement
‘s bound engine,
if any.
compile_kwargs¶ –
optional dictionary of additional parameters
that will be passed through to the compiler within all “visit”
methods. This allows any custom flag to be passed through to
a custom compilation construct, for example. It is also used
for the case of passing the literal_binds
flag through:
from sqlalchemy.sql import table, column, select
t = table('t', column('x'))
s = select(t).where(t.c.x == 5)
print(s.compile(compile_kwargs={"literal_binds": True}))
New in version 0.9.0.
sqlalchemy.sql.expression.TextualSelect.
corresponding_column(column, require_embedded=False)¶inherited from the Selectable.corresponding_column()
method of Selectable
Given a ColumnElement
, return the exported
ColumnElement
object from the
Selectable.exported_columns
collection of this Selectable
which corresponds to that
original ColumnElement
via a common ancestor
column.
column¶ – the target ColumnElement
to be matched.
require_embedded¶ – only return corresponding columns for
the given ColumnElement
, if the given
ColumnElement
is actually present within a sub-element
of this Selectable
.
Normally the column will match if
it merely shares a common ancestor with one of the exported
columns of this Selectable
.
See also
Selectable.exported_columns
- the
ColumnCollection
that is used for the operation.
ColumnCollection.corresponding_column()
- implementation
method.
sqlalchemy.sql.expression.TextualSelect.
cte(name=None, recursive=False)¶inherited from the HasCTE.cte()
method of HasCTE
Return a new CTE
,
or Common Table Expression instance.
Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
CTEs can also be applied to DML constructs UPDATE, INSERT and DELETE on some databases, both as a source of CTE rows when combined with RETURNING, as well as a consumer of CTE rows.
Changed in version 1.1: Added support for UPDATE/INSERT/DELETE as CTE, CTEs added to UPDATE/INSERT/DELETE.
SQLAlchemy detects CTE
objects, which are treated
similarly to Alias
objects, as special elements
to be delivered to the FROM clause of the statement as well
as to a WITH clause at the top of the statement.
For special prefixes such as PostgreSQL “MATERIALIZED” and
“NOT MATERIALIZED”, the CTE.prefix_with()
method may be
used to establish these.
Changed in version 1.3.13: Added support for prefixes. In particular - MATERIALIZED and NOT MATERIALIZED.
name¶ – name given to the common table expression. Like
FromClause.alias()
, the name can be left as
None
in which case an anonymous symbol will be used at query
compile time.
recursive¶ – if True
, will render WITH RECURSIVE
.
A recursive common table expression is intended to be used in
conjunction with UNION ALL in order to derive rows
from those already selected.
The following examples include two from PostgreSQL’s documentation at http://www.postgresql.org/docs/current/static/queries-with.html, as well as additional examples.
Example 1, non recursive:
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
orders = Table('orders', metadata,
Column('region', String),
Column('amount', Integer),
Column('product', String),
Column('quantity', Integer)
)
regional_sales = select(
orders.c.region,
func.sum(orders.c.amount).label('total_sales')
).group_by(orders.c.region).cte("regional_sales")
top_regions = select(regional_sales.c.region).\
where(
regional_sales.c.total_sales >
select(
func.sum(regional_sales.c.total_sales) / 10
)
).cte("top_regions")
statement = select(
orders.c.region,
orders.c.product,
func.sum(orders.c.quantity).label("product_units"),
func.sum(orders.c.amount).label("product_sales")
).where(orders.c.region.in_(
select(top_regions.c.region)
)).group_by(orders.c.region, orders.c.product)
result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
parts = Table('parts', metadata,
Column('part', String),
Column('sub_part', String),
Column('quantity', Integer),
)
included_parts = select(\
parts.c.sub_part, parts.c.part, parts.c.quantity\
).\
where(parts.c.part=='our part').\
cte(recursive=True)
incl_alias = included_parts.alias()
parts_alias = parts.alias()
included_parts = included_parts.union_all(
select(
parts_alias.c.sub_part,
parts_alias.c.part,
parts_alias.c.quantity
).\
where(parts_alias.c.part==incl_alias.c.sub_part)
)
statement = select(
included_parts.c.sub_part,
func.sum(included_parts.c.quantity).
label('total_quantity')
).\
group_by(included_parts.c.sub_part)
result = conn.execute(statement).fetchall()
Example 3, an upsert using UPDATE and INSERT with CTEs:
from datetime import date
from sqlalchemy import (MetaData, Table, Column, Integer,
Date, select, literal, and_, exists)
metadata = MetaData()
visitors = Table('visitors', metadata,
Column('product_id', Integer, primary_key=True),
Column('date', Date, primary_key=True),
Column('count', Integer),
)
# add 5 visitors for the product_id == 1
product_id = 1
day = date.today()
count = 5
update_cte = (
visitors.update()
.where(and_(visitors.c.product_id == product_id,
visitors.c.date == day))
.values(count=visitors.c.count + count)
.returning(literal(1))
.cte('update_cte')
)
upsert = visitors.insert().from_select(
[visitors.c.product_id, visitors.c.date, visitors.c.count],
select(literal(product_id), literal(day), literal(count))
.where(~exists(update_cte.select()))
)
connection.execute(upsert)
See also
Query.cte()
- ORM version of
HasCTE.cte()
.
sqlalchemy.sql.expression.TextualSelect.
execute(*multiparams, **params)¶inherited from the Executable.execute()
method of Executable
Compile and execute this Executable
.
Deprecated since version 1.4: The Executable.execute()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. All statement execution in SQLAlchemy 2.0 is performed by the Connection.execute()
method of Connection
, or in the ORM by the Session.execute()
method of Session
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.TextualSelect.
execution_options(**kw)¶inherited from the Executable.execution_options()
method of Executable
Set non-SQL options for the statement which take effect during execution.
Execution options can be set on a per-statement or
per Connection
basis. Additionally, the
Engine
and ORM Query
objects provide
access to execution options which they in turn configure upon
connections.
The execution_options()
method is generative. A new
instance of this statement is returned that contains the options:
statement = select(table.c.x, table.c.y)
statement = statement.execution_options(autocommit=True)
Note that only a subset of possible execution options can be applied
to a statement - these include “autocommit” and “stream_results”,
but not “isolation_level” or “compiled_cache”.
See Connection.execution_options()
for a full list of
possible options.
sqlalchemy.sql.expression.TextualSelect.
exists()¶inherited from the SelectBase.exists()
method of SelectBase
Return an Exists
representation of this selectable,
which can be used as a column expression.
The returned object is an instance of Exists
.
New in version 1.4.
sqlalchemy.sql.expression.TextualSelect.
exported_columns¶inherited from the SelectBase.exported_columns
attribute of SelectBase
A ColumnCollection
that represents the “exported”
columns of this Selectable
, not including
TextClause
constructs.
The “exported” columns for a SelectBase
object are synonymous
with the SelectBase.selected_columns
collection.
New in version 1.4.
sqlalchemy.sql.expression.TextualSelect.
get_children(omit_attrs=(), **kw)¶inherited from the ClauseElement.get_children()
method of ClauseElement
Return immediate child Traversible
elements of this Traversible
.
This is used for visit traversal.
**kw may contain flags that change the collection that is returned, for example to return a subset of items in order to cut down on larger traversals, or to return child items from a different context (such as schema-level collections instead of clause-level).
sqlalchemy.sql.expression.TextualSelect.
get_execution_options()¶inherited from the Executable.get_execution_options()
method of Executable
Get the non-SQL options which will take effect during execution.
New in version 1.3.
See also
sqlalchemy.sql.expression.TextualSelect.
label(name)¶inherited from the SelectBase.label()
method of SelectBase
Return a ‘scalar’ representation of this selectable, embedded as a subquery with a label.
See also
sqlalchemy.sql.expression.TextualSelect.
lateral(name=None)¶inherited from the SelectBase.lateral()
method of SelectBase
Return a LATERAL alias of this Selectable
.
The return value is the Lateral
construct also
provided by the top-level lateral()
function.
New in version 1.1.
See also
LATERAL correlation - overview of usage.
A read-only @property that is only evaluated once.
sqlalchemy.sql.expression.TextualSelect.
classmethod memoized_instancemethod(fn)¶inherited from the HasMemoized.memoized_instancemethod()
method of HasMemoized
Decorate a method memoize its return value.
sqlalchemy.sql.expression.TextualSelect.
options(*options)¶inherited from the Executable.options()
method of Executable
Apply options to this statement.
In the general sense, options are any kind of Python object that can be interpreted by the SQL compiler for the statement. These options can be consumed by specific dialects or specific kinds of compilers.
The most commonly known kind of option are the ORM level options that apply “eager load” and other loading behaviors to an ORM query. However, options can theoretically be used for many other purposes.
For background on specific kinds of options for specific kinds of statements, refer to the documentation for those option objects.
Changed in version 1.4: - added Generative.options()
to
Core statement objects towards the goal of allowing unified
Core / ORM querying capabilities.
See also
Deferred Column Loader Query Options - refers to options specific to the usage of ORM queries
Relationship Loading with Loader Options - refers to options specific to the usage of ORM queries
sqlalchemy.sql.expression.TextualSelect.
params(*optionaldict, **kwargs)¶inherited from the ClauseElement.params()
method of ClauseElement
Return a copy with bindparam()
elements
replaced.
Returns a copy of this ClauseElement with
bindparam()
elements replaced with values taken from the given dictionary:
>>> clause = column('x') + bindparam('foo')
>>> print(clause.compile().params)
{'foo':None}
>>> print(clause.params({'foo':7}).compile().params)
{'foo':7}
sqlalchemy.sql.expression.TextualSelect.
replace_selectable(old, alias)¶inherited from the Selectable.replace_selectable()
method of Selectable
Replace all occurrences of FromClause
‘old’ with the given Alias
object, returning a copy of this FromClause
.
Deprecated since version 1.4: The Selectable.replace_selectable()
method is deprecated, and will be removed in a future release. Similar functionality is available via the sqlalchemy.sql.visitors module.
sqlalchemy.sql.expression.TextualSelect.
scalar(*multiparams, **params)¶inherited from the Executable.scalar()
method of Executable
Compile and execute this Executable
, returning the
result’s scalar representation.
Deprecated since version 1.4: The Executable.scalar()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Scalar execution in SQLAlchemy 2.0 is performed by the Connection.scalar()
method of Connection
, or in the ORM by the Session.scalar()
method of Session
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)
sqlalchemy.sql.expression.TextualSelect.
scalar_subquery()¶inherited from the SelectBase.scalar_subquery()
method of SelectBase
Return a ‘scalar’ representation of this selectable, which can be used as a column expression.
The returned object is an instance of ScalarSelect
.
Typically, a select statement which has only one column in its columns clause is eligible to be used as a scalar expression. The scalar subquery can then be used in the WHERE clause or columns clause of an enclosing SELECT.
Note that the scalar subquery differentiates from the FROM-level
subquery that can be produced using the
SelectBase.subquery()
method.
See also
Scalar and Correlated Subqueries - in the 2.0 tutorial
Scalar Selects - in the 1.x tutorial
sqlalchemy.sql.expression.TextualSelect.
select(*arg, **kw)¶inherited from the SelectBase.select()
method of SelectBase
Deprecated since version 1.4: The SelectBase.select()
method is deprecated and will be removed in a future release; this method implicitly creates a subquery that should be explicit. Please call SelectBase.subquery()
first in order to create a subquery, which then can be selected.
sqlalchemy.sql.expression.TextualSelect.
selected_columns¶A ColumnCollection
representing the columns that
this SELECT statement or similar construct returns in its result set,
not including TextClause
constructs.
This collection differs from the FromClause.columns
collection of a FromClause
in that the columns
within this collection cannot be directly nested inside another SELECT
statement; a subquery must be applied first which provides for the
necessary parenthesization required by SQL.
For a TextualSelect
construct, the collection
contains the ColumnElement
objects that were
passed to the constructor, typically via the
TextClause.columns()
method.
New in version 1.4.
sqlalchemy.sql.expression.TextualSelect.
self_group(against: Optional[Any] = None) → ClauseElement¶inherited from the ClauseElement.self_group()
method of ClauseElement
Apply a ‘grouping’ to this ClauseElement
.
This method is overridden by subclasses to return a “grouping”
construct, i.e. parenthesis. In particular it’s used by “binary”
expressions to provide a grouping around themselves when placed into a
larger expression, as well as by select()
constructs when placed into the FROM clause of another
select()
. (Note that subqueries should be
normally created using the Select.alias()
method,
as many
platforms require nested SELECT statements to be named).
As expressions are composed together, the application of
self_group()
is automatic - end-user code should never
need to use this method directly. Note that SQLAlchemy’s
clause constructs take operator precedence into account -
so parenthesis might not be needed, for example, in
an expression like x OR (y AND z)
- AND takes precedence
over OR.
The base self_group()
method of
ClauseElement
just returns self.
sqlalchemy.sql.expression.TextualSelect.
subquery(name=None)¶inherited from the SelectBase.subquery()
method of SelectBase
Return a subquery of this SelectBase
.
A subquery is from a SQL perspective a parenthesized, named construct that can be placed in the FROM clause of another SELECT statement.
Given a SELECT statement such as:
stmt = select(table.c.id, table.c.name)
The above statement might look like:
SELECT table.id, table.name FROM table
The subquery form by itself renders the same way, however when embedded into the FROM clause of another SELECT statement, it becomes a named sub-element:
subq = stmt.subquery()
new_stmt = select(subq)
The above renders as:
SELECT anon_1.id, anon_1.name
FROM (SELECT table.id, table.name FROM table) AS anon_1
Historically, SelectBase.subquery()
is equivalent to calling
the FromClause.alias()
method on a FROM object; however,
as a SelectBase
object is not directly FROM object,
the SelectBase.subquery()
method provides clearer semantics.
New in version 1.4.
sqlalchemy.sql.expression.TextualSelect.
unique_params(*optionaldict, **kwargs)¶inherited from the ClauseElement.unique_params()
method of ClauseElement
Return a copy with bindparam()
elements
replaced.
Same functionality as ClauseElement.params()
,
except adds unique=True
to affected bind parameters so that multiple statements can be
used.
Represent a VALUES
construct that can be used as a FROM element
in a statement.
The Values
object is created from the
values()
function.
New in version 1.4.
Class signature
class sqlalchemy.sql.expression.Values
(sqlalchemy.sql.expression.Generative
, sqlalchemy.sql.expression.FromClause
)
sqlalchemy.sql.expression.Values.
__init__(*columns, **kw)¶Construct a new Values
object.
This constructor is mirrored as a public API function; see sqlalchemy.sql.expression.values()
for a full usage and argument description.
sqlalchemy.sql.expression.Values.
alias(name, **kw)¶Return a new Values
construct that is a copy of this
one with the given name.
This method is a VALUES-specific specialization of the
FromClause.alias()
method.
sqlalchemy.sql.expression.Values.
data(values)¶Return a new Values
construct,
adding the given data
to the data list.
E.g.:
my_values = my_values.data([(1, 'value 1'), (2, 'value2')])
sqlalchemy.sql.expression.Values.
lateral(name=None)¶Return a new Values
with the lateral flag set,
so that
it renders as LATERAL.
See also
Constants used with the GenerativeSelect.set_label_style()
method.
Object Name | Description |
---|---|
The default label style, refers to |
|
Label style indicating that columns with a name that conflicts with an existing name should be labeled with a semi-anonymizing label when generating the columns clause of a SELECT statement. |
|
Label style indicating no automatic labeling should be applied to the columns clause of a SELECT statement. |
|
Label style indicating all columns should be labeled as
|
Label style indicating that columns with a name that conflicts with an existing name should be labeled with a semi-anonymizing label when generating the columns clause of a SELECT statement.
Below, most column names are left unaffected, except for the second
occurrence of the name columna
, which is labeled using the
label columna_1
to disambiguate it from that of tablea.columna
:
>>> from sqlalchemy import table, column, select, true, LABEL_STYLE_DISAMBIGUATE_ONLY
>>> table1 = table("table1", column("columna"), column("columnb"))
>>> table2 = table("table2", column("columna"), column("columnc"))
>>> print(select(table1, table2).join(table2, true()).set_label_style(LABEL_STYLE_DISAMBIGUATE_ONLY))
SELECT table1.columna, table1.columnb, table2.columna AS columna_1, table2.columnc
FROM table1 JOIN table2 ON true
Used with the GenerativeSelect.set_label_style()
method,
LABEL_STYLE_DISAMBIGUATE_ONLY
is the default labeling style
for all SELECT statements outside of 1.x style ORM queries.
New in version 1.4.
Label style indicating no automatic labeling should be applied to the columns clause of a SELECT statement.
Below, the columns named columna
are both rendered as is, meaning that
the name columna
can only refer to the first occurrence of this name
within a result set, as well as if the statement were used as a subquery:
>>> from sqlalchemy import table, column, select, true, LABEL_STYLE_NONE
>>> table1 = table("table1", column("columna"), column("columnb"))
>>> table2 = table("table2", column("columna"), column("columnc"))
>>> print(select(table1, table2).join(table2, true()).set_label_style(LABEL_STYLE_NONE))
SELECT table1.columna, table1.columnb, table2.columna, table2.columnc
FROM table1 JOIN table2 ON true
Used with the Select.set_label_style()
method.
New in version 1.4.
Label style indicating all columns should be labeled as
<tablename>_<columnname>
when generating the columns clause of a SELECT
statement, to disambiguate same-named columns referenced from different
tables, aliases, or subqueries.
Below, all column names are given a label so that the two same-named
columns columna
are disambiguated as table1_columna
and
``table2_columna`:
>>> from sqlalchemy import table, column, select, true, LABEL_STYLE_TABLENAME_PLUS_COL
>>> table1 = table("table1", column("columna"), column("columnb"))
>>> table2 = table("table2", column("columna"), column("columnc"))
>>> print(select(table1, table2).join(table2, true()).set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL))
SELECT table1.columna AS table1_columna, table1.columnb AS table1_columnb, table2.columna AS table2_columna, table2.columnc AS table2_columnc
FROM table1 JOIN table2 ON true
Used with the GenerativeSelect.set_label_style()
method.
Equivalent to the legacy method Select.apply_labels()
;
LABEL_STYLE_TABLENAME_PLUS_COL
is SQLAlchemy’s legacy
auto-labeling style. LABEL_STYLE_DISAMBIGUATE_ONLY
provides a
less intrusive approach to disambiguation of same-named column expressions.
New in version 1.4.
The default label style, refers to LABEL_STYLE_DISAMBIGUATE_ONLY
.
New in version 1.4.
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