Release: 1.4.39 | Release Date: June 24, 2022

# SQLAlchemy 1.4 Documentation

# Query API

This section presents the API reference for the ORM `Query` object. For a walkthrough of how to use this object, see Object Relational Tutorial (1.x API).

## The Query Object

`Query` is produced in terms of a given `Session`, using the `Session.query()` method:

    q = session.query(SomeMappedClass)

Following is the full interface for the `Query` object.

Object Name | Description
--- | ---
Query | ORM-level SQL construction object.

class sqlalchemy.orm.Query(entities, session=None)

  ORM-level SQL construction object.

  `Query` is the source of all SELECT statements generated by the ORM, both those formulated by end-user query operations as well as by high level internal operations such as related collection loading. It features a generative interface whereby successive calls return a new `Query` object, a copy of the former with additional criteria and options associated with it.

  `Query` objects are normally initially generated using the `Session.query()` method of `Session`, and in less common cases by instantiating the `Query` directly and associating with a `Session` using the `Query.with_session()` method.

  For a full walk through of `Query` usage, see the Object Relational Tutorial (1.x API).

  Class signature

  class `sqlalchemy.orm.Query` (`sqlalchemy.sql.expression._SelectFromElements`, `sqlalchemy.sql.annotation.SupportsCloneAnnotations`, `sqlalchemy.sql.expression.HasPrefixes`, `sqlalchemy.sql.expression.HasSuffixes`, `sqlalchemy.sql.expression.HasHints`, `sqlalchemy.sql.expression.Executable`)

  method `sqlalchemy.orm.Query.`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()`.

    Parameters

      - *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.

  method `sqlalchemy.orm.Query.`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()`.

    Parameters

      - *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.

  method `sqlalchemy.orm.Query.`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

    `Select.with_statement_hint()`

  method `sqlalchemy.orm.Query.`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.with_hint()`

    `Select.prefix_with()` - generic SELECT prefixing which also can suit some database-specific HINT syntaxes such as MySQL optimizer hints

  method `sqlalchemy.orm.Query.`__init__(entities, session=None)

    Construct a `Query` directly.

    E.g.:

        q = Query([User, Address], session=some_session)

    The above is equivalent to:

        q = some_session.query(User, Address)

    Parameters

      - entities – a sequence of entities and/or SQL expressions.

      - session – a `Session` with which the `Query` will be associated. Optional; a `Query` can be associated with a `Session` generatively via the `Query.with_session()` method as well.

    See also

    `Session.query()`

    `Query.with_session()`

  method `sqlalchemy.orm.Query.`add_column(column)

    Add a column expression to the list of result columns to be returned.

    Deprecated since version 1.4: `Query.add_column()` is deprecated and will be removed in a future release. Please use `Query.add_columns()`

  method `sqlalchemy.orm.Query.`add_columns(*column)

    Add one or more column expressions to the list of result columns to be returned.

  method `sqlalchemy.orm.Query.`add_entity(entity, alias=None)

    add a mapped entity to the list of result columns to be returned.

  method `sqlalchemy.orm.Query.`all()

    Return the results represented by this `Query` as a list.

    This results in an execution of the underlying SQL statement.

    Warning

    The `Query` object, when asked to return either a sequence or iterator that consists of full ORM-mapped entities, will deduplicate entries based on primary key. See the FAQ for more details.

    > See also

    > My Query does not return the same number of objects as query.count() tells me - why?

  method `sqlalchemy.orm.Query.`apply_labels()

    Deprecated since version 1.4: The `Query.with_labels()` and `Query.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)

  method `sqlalchemy.orm.Query.`as_scalar()

    Return the full SELECT statement represented by this `Query`, converted to a scalar subquery.

    Deprecated since version 1.4: The `Query.as_scalar()` method is deprecated and will be removed in a future release. Please refer to `Query.scalar_subquery()`.

  method `sqlalchemy.orm.Query.`autoflush(setting)

    Return a Query with a specific ‘autoflush’ setting.

    As of SQLAlchemy 1.4, the `Query.autoflush()` method is equivalent to using the `autoflush` execution option at the ORM level. See the section Autoflush for further background on this option.

  attribute `sqlalchemy.orm.Query.`column_descriptions

    Return metadata about the columns which would be returned by this `Query`.

    Format is a list of dictionaries:

        user_alias = aliased(User, name='user2')
        q = sess.query(User, User.id, user_alias)

        # this expression:
        q.column_descriptions

        # would return:
        [
            {
                'name':'User',
                'type':User,
                'aliased':False,
                'expr':User,
                'entity': User
            },
            {
                'name':'id',
                'type':Integer(),
                'aliased':False,
                'expr':User.id,
                'entity': User
            },
            {
                'name':'user2',
                'type':User,
                'aliased':True,
                'expr':user_alias,
                'entity': user_alias
            }
        ]

    See also

    This API is available using 2.0 style queries as well, documented at:

    - Inspecting entities and columns from ORM-enabled SELECT and DML statements

    - `Select.column_descriptions`

  method `sqlalchemy.orm.Query.`correlate(*fromclauses)

    Return a `Query` construct which will correlate the given FROM clauses to that of an enclosing `Query` or `select()`.

    The method here accepts mapped classes, `aliased()` constructs, and `mapper()` constructs as arguments, which are resolved into expression constructs, in addition to appropriate expression constructs.

    The correlation arguments are ultimately passed to `Select.correlate()` after coercion to expression constructs.

    The correlation arguments take effect in such cases as when `Query.from_self()` is used, or when a subquery as returned by `Query.subquery()` is embedded in another `select()` construct.

  method `sqlalchemy.orm.Query.`count()

    Return a count of rows this the SQL formed by this `Query` would return.

    This generates the SQL for this Query as follows:

        SELECT count(1) AS count_1 FROM (
            SELECT <rest of query follows...>
        ) AS anon_1

    The above SQL returns a single row, which is the aggregate value of the count function; the `Query.count()` method then returns that single integer value.

    Warning

    It is important to note that the value returned by count() is not the same as the number of ORM objects that this Query would return from a method such as the .all() method. The `Query` object, when asked to return full entities, will deduplicate entries based on primary key, meaning if the same primary key value would appear in the results more than once, only one object of that primary key would be present. This does not apply to a query that is against individual columns.

    See also

    My Query does not return the same number of objects as query.count() tells me - why?

    Returning Lists and Scalars

    For fine grained control over specific columns to count, to skip the usage of a subquery or otherwise control of the FROM clause, or to use other aggregate functions, use `expression.func` expressions in conjunction with `Session.query()`, i.e.:

        from sqlalchemy import func

        # count User records, without
        # using a subquery.
        session.query(func.count(User.id))

        # return count of user "id" grouped
        # by "name"
        session.query(func.count(User.id)).\
                group_by(User.name)

        from sqlalchemy import distinct

        # count distinct "name" values
        session.query(func.count(distinct(User.name)))

  method `sqlalchemy.orm.Query.`cte(name=None, recursive=False, nesting=False)

    Return the full SELECT statement represented by this `Query` represented as a common table expression (CTE).

    Parameters and usage are the same as those of the `SelectBase.cte()` method; see that method for further details.

    Here is the PostgreSQL WITH RECURSIVE example. Note that, in this example, the `included_parts` cte and the `incl_alias` alias of it are Core selectables, which means the columns are accessed via the `.c.` attribute. The `parts_alias` object is an `aliased()` instance of the `Part` entity, so column-mapped attributes are available directly:

        from sqlalchemy.orm import aliased

        class Part(Base):
            __tablename__ = 'part'
            part = Column(String, primary_key=True)
            sub_part = Column(String, primary_key=True)
            quantity = Column(Integer)

        included_parts = session.query(
                        Part.sub_part,
                        Part.part,
                        Part.quantity).\
                            filter(Part.part=="our part").\
                            cte(name="included_parts", recursive=True)

        incl_alias = aliased(included_parts, name="pr")
        parts_alias = aliased(Part, name="p")
        included_parts = included_parts.union_all(
            session.query(
                parts_alias.sub_part,
                parts_alias.part,
                parts_alias.quantity).\
                    filter(parts_alias.part==incl_alias.c.sub_part)
            )

        q = session.query(
                included_parts.c.sub_part,
                func.sum(included_parts.c.quantity).
                    label('total_quantity')
            ).\
            group_by(included_parts.c.sub_part)

    See also

    `HasCTE.cte()`

  method `sqlalchemy.orm.Query.`delete(synchronize_session='evaluate')

    Perform a DELETE with an arbitrary WHERE clause.

    Deletes rows matched by this query from the database.

    E.g.:

        sess.query(User).filter(User.age == 25).\
            delete(synchronize_session=False)

        sess.query(User).filter(User.age == 25).\
            delete(synchronize_session='evaluate')

    Warning

    See the section UPDATE and DELETE with arbitrary WHERE clause for important caveats and warnings, including limitations when using bulk UPDATE and DELETE with mapper inheritance configurations.

    Parameters

      synchronize_session – chooses the strategy to update the attributes on objects in the session. See the section UPDATE and DELETE with arbitrary WHERE clause for a discussion of these strategies.

    Returns

      the count of rows matched as returned by the database’s “row count” feature.

    See also

    UPDATE and DELETE with arbitrary WHERE clause

  method `sqlalchemy.orm.Query.`distinct(*expr)

    Apply a `DISTINCT` to the query and return the newly resulting `Query`.

    Note

    The ORM-level `distinct()` call includes logic that will automatically add columns from the ORDER BY of the query to the columns clause of the SELECT statement, to satisfy the common need of the database backend that ORDER BY columns be part of the SELECT list when DISTINCT is used. These columns are not added to the list of columns actually fetched by the `Query`, however, so would not affect results. The columns are passed through when using the `Query.statement` accessor, however.

    Deprecated since version 2.0: This logic is deprecated and will be removed in SQLAlchemy 2.0. See Using DISTINCT with additional columns, but only select the entity for a description of this use case in 2.0.

    Parameters

      *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.

  method `sqlalchemy.orm.Query.`enable_assertions(value)

    Control whether assertions are generated.

    When set to False, the returned Query will not assert its state before certain operations, including that LIMIT/OFFSET has not been applied when filter() is called, no criterion exists when get() is called, and no “from_statement()” exists when filter()/order_by()/group_by() etc. is called. This more permissive mode is used by custom Query subclasses to specify criterion or other modifiers outside of the usual usage patterns.

    Care should be taken to ensure that the usage pattern is even possible. A statement applied by from_statement() will override any criterion set by filter() or order_by(), for example.

  method `sqlalchemy.orm.Query.`enable_eagerloads(value)

    Control whether or not eager joins and subqueries are rendered.

    When set to False, the returned Query will not render eager joins regardless of `joinedload()`, `subqueryload()` options or mapper-level `lazy='joined'`/`lazy='subquery'` configurations.

    This is used primarily when nesting the Query’s statement into a subquery or other selectable, or when using `Query.yield_per()`.

  method `sqlalchemy.orm.Query.`except_(*q)

    Produce an EXCEPT of this Query against one or more queries.

    Works the same way as `Query.union()`. See that method for usage examples.

  method `sqlalchemy.orm.Query.`except_all(*q)

    Produce an EXCEPT ALL of this Query against one or more queries.

    Works the same way as `Query.union()`. See that method for usage examples.

  method `sqlalchemy.orm.Query.`execution_options(**kwargs)

    Set non-SQL options which take effect during execution.

    Options allowed here include all of those accepted by `Connection.execution_options()`, as well as a series of ORM specific options:

    `populate_existing=True` - equivalent to using `Query.populate_existing()`

    `autoflush=True|False` - equivalent to using `Query.autoflush()`

    `yield_per=<value>` - equivalent to using `Query.yield_per()`

    Note that the `stream_results` execution option is enabled automatically if the `Query.yield_per()` method or execution option is used.

    New in version 1.4: - added ORM options to `Query.execution_options()`

    The execution options may also be specified on a per execution basis when using 2.0 style queries via the `Session.execution_options` parameter.

    Warning

    The `Connection.execution_options.stream_results` parameter should not be used at the level of individual ORM statement executions, as the `Session` will not track objects from different schema translate maps within a single session. For multiple schema translate maps within the scope of a single `Session`, see Horizontal Sharding.

    See also

    Using Server Side Cursors (a.k.a. stream results)

    `Query.get_execution_options()`

  method `sqlalchemy.orm.Query.`exists()

    A convenience method that turns a query into an EXISTS subquery of the form EXISTS (SELECT 1 FROM … WHERE …).

    e.g.:

        q = session.query(User).filter(User.name == 'fred')
        session.query(q.exists())

    Producing SQL similar to:

        SELECT EXISTS (
            SELECT 1 FROM users WHERE users.name = :name_1
        ) AS anon_1

    The EXISTS construct is usually used in the WHERE clause:

        session.query(User.id).filter(q.exists()).scalar()

    Note that some databases such as SQL Server don’t allow an EXISTS expression to be present in the columns clause of a SELECT. To select a simple boolean value based on the exists as a WHERE, use `literal()`:

        from sqlalchemy import literal

        session.query(literal(True)).filter(q.exists()).scalar()

  method `sqlalchemy.orm.Query.`filter(*criterion)

    Apply the given filtering criterion to a copy of this `Query`, using SQL expressions.

    e.g.:

        session.query(MyClass).filter(MyClass.name == 'some name')

    Multiple criteria may be specified as comma separated; the effect is that they will be joined together using the `and_()` function:

        session.query(MyClass).\
            filter(MyClass.name == 'some name', MyClass.id > 5)

    The criterion is any SQL expression object applicable to the WHERE clause of a select. String expressions are coerced into SQL expression constructs via the `text()` construct.

    See also

    `Query.filter_by()` - filter on keyword expressions.

  method `sqlalchemy.orm.Query.`filter_by(**kwargs)

    Apply the given filtering criterion to a copy of this `Query`, using keyword expressions.

    e.g.:

        session.query(MyClass).filter_by(name = 'some name')

    Multiple criteria may be specified as comma separated; the effect is that they will be joined together using the `and_()` function:

        session.query(MyClass).\
            filter_by(name = 'some name', id = 5)

    The keyword expressions are extracted from the primary entity of the query, or the last entity that was the target of a call to `Query.join()`.

    See also

    `Query.filter()` - filter on SQL expressions.

  method `sqlalchemy.orm.Query.`first()

    Return the first result of this `Query` or None if the result doesn’t contain any row.

    first() applies a limit of one within the generated SQL, so that only one primary entity row is generated on the server side (note this may consist of multiple result rows if join-loaded collections are present).

    Calling `Query.first()` results in an execution of the underlying query.

    See also

    `Query.one()`

    `Query.one_or_none()`

  method `sqlalchemy.orm.Query.`from_self(*entities)

    return a Query that selects from this Query’s SELECT statement.

    Deprecated since version 1.4: The `Query.from_self()` method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. The new approach is to use the `aliased()` construct in conjunction with a subquery. See the section Selecting from the query itself as a subquery in the 2.0 migration notes for an example. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)

    `Query.from_self()` essentially turns the SELECT statement into a SELECT of itself. Given a query such as:

        q = session.query(User).filter(User.name.like('e%'))

    Given the `Query.from_self()` version:

        q = session.query(User).filter(User.name.like('e%')).from_self()

    This query renders as:

        SELECT anon_1.user_id AS anon_1_user_id,
               anon_1.user_name AS anon_1_user_name
        FROM (SELECT "user".id AS user_id, "user".name AS user_name
        FROM "user"
        WHERE "user".name LIKE :name_1) AS anon_1

    There are lots of cases where `Query.from_self()` may be useful. A simple one is where above, we may want to apply a row LIMIT to the set of user objects we query against, and then apply additional joins against that row-limited set:

        q = session.query(User).filter(User.name.like('e%')).\
            limit(5).from_self().\
            join(User.addresses).filter(Address.email.like('q%'))

    The above query joins to the `Address` entity but only against the first five results of the `User` query:

        SELECT anon_1.user_id AS anon_1_user_id,
               anon_1.user_name AS anon_1_user_name
        FROM (SELECT "user".id AS user_id, "user".name AS user_name
        FROM "user"
        WHERE "user".name LIKE :name_1
         LIMIT :param_1) AS anon_1
        JOIN address ON anon_1.user_id = address.user_id
        WHERE address.email LIKE :email_1

    Automatic Aliasing

    Another key behavior of `Query.from_self()` is that it applies automatic aliasing to the entities inside the subquery, when they are referenced on the outside. Above, if we continue to refer to the `User` entity without any additional aliasing applied to it, those references will be in terms of the subquery:

        q = session.query(User).filter(User.name.like('e%')).\
            limit(5).from_self().\
            join(User.addresses).filter(Address.email.like('q%')).\
            order_by(User.name)

    The ORDER BY against `User.name` is aliased to be in terms of the inner subquery:

        SELECT anon_1.user_id AS anon_1_user_id,
               anon_1.user_name AS anon_1_user_name
        FROM (SELECT "user".id AS user_id, "user".name AS user_name
        FROM "user"
        WHERE "user".name LIKE :name_1
         LIMIT :param_1) AS anon_1
        JOIN address ON anon_1.user_id = address.user_id
        WHERE address.email LIKE :email_1 ORDER BY anon_1.user_name

    The automatic aliasing feature only works in a limited way, for simple filters and orderings. More ambitious constructions such as referring to the entity in joins should prefer to use explicit subquery objects, typically making use of the `Query.subquery()` method to produce an explicit subquery object. Always test the structure of queries by viewing the SQL to ensure a particular structure does what’s expected!

    Changing the Entities

    `Query.from_self()` also includes the ability to modify what columns are being queried. In our example, we want `User.id` to be queried by the inner query, so that we can join to the `Address` entity on the outside, but we only wanted the outer query to return the `Address.email` column:

        q = session.query(User).filter(User.name.like('e%')).\
            limit(5).from_self(Address.email).\
            join(User.addresses).filter(Address.email.like('q%'))

    yielding:

        SELECT address.email AS address_email
        FROM (SELECT "user".id AS user_id, "user".name AS user_name
        FROM "user"
        WHERE "user".name LIKE :name_1
         LIMIT :param_1) AS anon_1
        JOIN address ON anon_1.user_id = address.user_id
        WHERE address.email LIKE :email_1

    Looking out for Inner / Outer Columns

    Keep in mind that when referring to columns that originate from inside the subquery, we need to ensure they are present in the columns clause of the subquery itself; this is an ordinary aspect of SQL. For example, if we wanted to load from a joined entity inside the subquery using `contains_eager()`, we need to add those columns. Below illustrates a join of `Address` to `User`, then a subquery, and then we’d like `contains_eager()` to access the `User` columns:

        q = session.query(Address).join(Address.user).\
            filter(User.name.like('e%'))

        q = q.add_entity(User).from_self().\
            options(contains_eager(Address.user))

    We use `Query.add_entity()` above before we call `Query.from_self()` so that the `User` columns are present in the inner subquery, so that they are available to the `contains_eager()` modifier we are using on the outside, producing:

        SELECT anon_1.address_id AS anon_1_address_id,
               anon_1.address_email AS anon_1_address_email,
               anon_1.address_user_id AS anon_1_address_user_id,
               anon_1.user_id AS anon_1_user_id,
               anon_1.user_name AS anon_1_user_name
        FROM (
            SELECT address.id AS address_id,
            address.email AS address_email,
            address.user_id AS address_user_id,
            "user".id AS user_id,
            "user".name AS user_name
        FROM address JOIN "user" ON "user".id = address.user_id
        WHERE "user".name LIKE :name_1) AS anon_1

    If we didn’t call `add_entity(User)`, but still asked `contains_eager()` to load the `User` entity, it would be forced to add the table on the outside without the correct join criteria - note the `anon1, "user"` phrase at the end:

        -- incorrect query
        SELECT anon_1.address_id AS anon_1_address_id,
               anon_1.address_email AS anon_1_address_email,
               anon_1.address_user_id AS anon_1_address_user_id,
               "user".id AS user_id,
               "user".name AS user_name
        FROM (
            SELECT address.id AS address_id,
            address.email AS address_email,
            address.user_id AS address_user_id
        FROM address JOIN "user" ON "user".id = address.user_id
        WHERE "user".name LIKE :name_1) AS anon_1, "user"

    Parameters

      *entities – optional list of entities which will replace those being selected.

  method `sqlalchemy.orm.Query.`from_statement(statement)

    Execute the given SELECT statement and return results.

    This method bypasses all internal statement compilation, and the statement is executed without modification.

    The statement is typically either a `text()` or `select()` construct, and should return the set of columns appropriate to the entity class represented by this `Query`.

    See also

    Using Textual SQL - usage examples in the ORM tutorial

  method `sqlalchemy.orm.Query.`get(ident)

    Return an instance based on the given primary key identifier, or `None` if not found.

    Deprecated since version 1.4: The `Query.get()` method is considered legacy as of the 1.x series of SQLAlchemy and becomes a legacy construct in 2.0. The method is now available as `Session.get()` (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)

    E.g.:

        my_user = session.query(User).get(5)

        some_object = session.query(VersionedFoo).get((5, 10))

        some_object = session.query(VersionedFoo).get(
            {"id": 5, "version_id": 10})

    `Query.get()` is special in that it provides direct access to the identity map of the owning `Session`. If the given primary key identifier is present in the local identity map, the object is returned directly from this collection and no SQL is emitted, unless the object has been marked fully expired. If not present, a SELECT is performed in order to locate the object.

    `Query.get()` also will perform a check if the object is present in the identity map and marked as expired - a SELECT is emitted to refresh the object as well as to ensure that the row is still present. If not, `ObjectDeletedError` is raised.

    `Query.get()` is only used to return a single mapped instance, not multiple instances or individual column constructs, and strictly on a single primary key value. The originating `Query` must be constructed in this way, i.e. against a single mapped entity, with no additional filtering criterion. Loading options via `Query.options()` may be applied however, and will be used if the object is not yet locally present.

    Parameters

      ident –

      A scalar, tuple, or dictionary representing the primary key. For a composite (e.g. multiple column) primary key, a tuple or dictionary should be passed.

      For a single-column primary key, the scalar calling form is typically the most expedient. If the primary key of a row is the value “5”, the call looks like:

          my_object = query.get(5)

      The tuple form contains primary key values typically in the order in which they correspond to the mapped `Table` object’s primary key columns, or if the `Mapper.primary_key` configuration parameter were used, in the order used for that parameter. For example, if the primary key of a row is represented by the integer digits “5, 10” the call would look like:

          my_object = query.get((5, 10))

      The dictionary form should include as keys the mapped attribute names corresponding to each element of the primary key. If the mapped class has the attributes `id`, `version_id` as the attributes which store the object’s primary key value, the call would look like:

          my_object = query.get({"id": 5, "version_id": 10})

      New in version 1.3: the `Query.get()` method now optionally accepts a dictionary of attribute names to values in order to indicate a primary key identifier.

    Returns

      The object instance, or `None`.

  method `sqlalchemy.orm.Query.`get_execution_options()

    Get the non-SQL options which will take effect during execution.

    New in version 1.3.

    See also

    `Query.execution_options()`

  attribute `sqlalchemy.orm.Query.`get_label_style

    Retrieve the current label style.

    New in version 1.4.

  method `sqlalchemy.orm.Query.`group_by(*clauses)

    Apply one or more GROUP BY criterion to the query and return the newly resulting `Query`.

    All existing GROUP BY settings can be suppressed by passing `None` - this will suppress any GROUP BY configured on mappers as well.

    See also

    These sections describe GROUP BY in terms of 2.0 style invocation but apply to `Query` as well:

    Aggregate functions with GROUP BY / HAVING - in the SQLAlchemy 1.4 / 2.0 Tutorial

    Ordering or Grouping by a Label - in the SQLAlchemy 1.4 / 2.0 Tutorial

  method `sqlalchemy.orm.Query.`having(criterion)

    Apply a HAVING criterion to the query and return the newly resulting `Query`.

    `Query.having()` is used in conjunction with `Query.group_by()`.

    HAVING criterion makes it possible to use filters on aggregate functions like COUNT, SUM, AVG, MAX, and MIN, eg.:

        q = session.query(User.id).\
                    join(User.addresses).\
                    group_by(User.id).\
                    having(func.count(Address.id) > 2)

  method `sqlalchemy.orm.Query.`instances(result_proxy, context=None)

    Return an ORM result given a `CursorResult` and `QueryContext`.

  method `sqlalchemy.orm.Query.`intersect(*q)

    Produce an INTERSECT of this Query against one or more queries.

    Works the same way as `Query.union()`. See that method for usage examples.

  method `sqlalchemy.orm.Query.`intersect_all(*q)

    Produce an INTERSECT ALL of this Query against one or more queries.

    Works the same way as `Query.union()`. See that method for usage examples.

  attribute `sqlalchemy.orm.Query.`is_single_entity

    Indicates if this `Query` returns tuples or single entities.

    Returns True if this query returns a single entity for each instance in its result list, and False if this query returns a tuple of entities for each result.

    New in version 1.3.11.

    See also

    `Query.only_return_tuples()`

  method `sqlalchemy.orm.Query.`join(target, *props, **kwargs)

    Create a SQL JOIN against this `Query` object’s criterion and apply generatively, returning the newly resulting `Query`.

    Simple Relationship Joins

    Consider a mapping between two classes `User` and `Address`, with a relationship `User.addresses` representing a collection of `Address` objects associated with each `User`. The most common usage of `Query.join()` is to create a JOIN along this relationship, using the `User.addresses` attribute as an indicator for how this should occur:

        q = session.query(User).join(User.addresses)

    Where above, the call to `Query.join()` along `User.addresses` will result in SQL approximately equivalent to:

        SELECT user.id, user.name
        FROM user JOIN address ON user.id = address.user_id

    In the above example we refer to `User.addresses` as passed to `Query.join()` as the “on clause”, that is, it indicates how the “ON” portion of the JOIN should be constructed.

    To construct a chain of joins, multiple `Query.join()` calls may be used. The relationship-bound attribute implies both the left and right side of the join at once:

        q = session.query(User).\
                join(User.orders).\
                join(Order.items).\
                join(Item.keywords)

    Note

    as seen in the above example, the order in which each call to the join() method occurs is important. Query would not, for example, know how to join correctly if we were to specify `User`, then `Item`, then `Order`, in our chain of joins; in such a case, depending on the arguments passed, it may raise an error that it doesn’t know how to join, or it may produce invalid SQL in which case the database will raise an error. In correct practice, the `Query.join()` method is invoked in such a way that lines up with how we would want the JOIN clauses in SQL to be rendered, and each call should represent a clear link from what precedes it.

    Joins to a Target Entity or Selectable

    A second form of `Query.join()` allows any mapped entity or core selectable construct as a target. In this usage, `Query.join()` will attempt to create a JOIN along the natural foreign key relationship between two entities:

        q = session.query(User).join(Address)

    In the above calling form, `Query.join()` is called upon to create the “on clause” automatically for us. This calling form will ultimately raise an error if either there are no foreign keys between the two entities, or if there are multiple foreign key linkages between the target entity and the entity or entities already present on the left side such that creating a join requires more information. Note that when indicating a join to a target without any ON clause, ORM configured relationships are not taken into account.

    Joins to a Target with an ON Clause

    The third calling form allows both the target entity as well as the ON clause to be passed explicitly. A example that includes a SQL expression as the ON clause is as follows:

        q = session.query(User).join(Address, User.id==Address.user_id)

    The above form may also use a relationship-bound attribute as the ON clause as well:

        q = session.query(User).join(Address, User.addresses)

    The above syntax can be useful for the case where we wish to join to an alias of a particular target entity. If we wanted to join to `Address` twice, it could be achieved using two aliases set up using the `aliased()` function:

        a1 = aliased(Address)
        a2 = aliased(Address)

        q = session.query(User).\
                join(a1, User.addresses).\
                join(a2, User.addresses).\
                filter(a1.email_address=='ed@foo.com').\
                filter(a2.email_address=='ed@bar.com')

    The relationship-bound calling form can also specify a target entity using the `PropComparator.of_type()` method; a query equivalent to the one above would be:

        a1 = aliased(Address)
        a2 = aliased(Address)

        q = session.query(User).\
                join(User.addresses.of_type(a1)).\
                join(User.addresses.of_type(a2)).\
                filter(a1.email_address == 'ed@foo.com').\
                filter(a2.email_address == 'ed@bar.com')

    Augmenting Built-in ON Clauses

    As a substitute for providing a full custom ON condition for an existing relationship, the `PropComparator.and_()` function may be applied to a relationship attribute to augment additional criteria into the ON clause; the additional criteria will be combined with the default criteria using AND:

        q = session.query(User).join(
            User.addresses.and_(Address.email_address != 'foo@bar.com')
        )

    New in version 1.4.

    Joining to Tables and Subqueries

    The target of a join may also be any table or SELECT statement, which may be related to a target entity or not. Use the appropriate `.subquery()` method in order to make a subquery out of a query:

        subq = session.query(Address).\
            filter(Address.email_address == 'ed@foo.com').\
            subquery()

        q = session.query(User).join(
            subq, User.id == subq.c.user_id
        )

    Joining to a subquery in terms of a specific relationship and/or target entity may be achieved by linking the subquery to the entity using `aliased()`:

        subq = session.query(Address).\
            filter(Address.email_address == 'ed@foo.com').\
            subquery()

        address_subq = aliased(Address, subq)

        q = session.query(User).join(
            User.addresses.of_type(address_subq)
        )

    Controlling what to Join From

    In cases where the left side of the current state of `Query` is not in line with what we want to join from, the `Query.select_from()` method may be used:

        q = session.query(Address).select_from(User).\
                        join(User.addresses).\
                        filter(User.name == 'ed')

    Which will produce SQL similar to:

        SELECT address.* FROM user
            JOIN address ON user.id=address.user_id
            WHERE user.name = :name_1

    Legacy Features of Query.join()

    Deprecated since version 1.4: The following features are deprecated and will be removed in SQLAlchemy 2.0.

    The `Query.join()` method currently supports several usage patterns and arguments that are considered to be legacy as of SQLAlchemy 1.3. A deprecation path will follow in the 1.4 series for the following features:

    - Joining on relationship names rather than attributes:

          session.query(User).join("addresses")

      Why it’s legacy: the string name does not provide enough context for `Query.join()` to always know what is desired, notably in that there is no indication of what the left side of the join should be. This gives rise to flags like `from_joinpoint` as well as the ability to place several join clauses in a single `Query.join()` call which don’t solve the problem fully while also adding new calling styles that are unnecessary and expensive to accommodate internally.

      Modern calling pattern: Use the actual relationship, e.g. `User.addresses` in the above case:

          session.query(User).join(User.addresses)

    - Automatic aliasing with the `aliased=True` flag:

          session.query(Node).join(Node.children, aliased=True).\
              filter(Node.name == 'some name')

      Why it’s legacy: the automatic aliasing feature of `Query` is intensely complicated, both in its internal implementation as well as in its observed behavior, and is almost never used. It is difficult to know upon inspection where and when its aliasing of a target entity, `Node` in the above case, will be applied and when it won’t, and additionally the feature has to use very elaborate heuristics to achieve this implicit behavior.

      Modern calling pattern: Use the `aliased()` construct explicitly:

          from sqlalchemy.orm import aliased

          n1 = aliased(Node)

          session.query(Node).join(Node.children.of_type(n1)).\
              filter(n1.name == 'some name')

    - Multiple joins in one call:

          session.query(User).join("orders", "items")

          session.query(User).join(User.orders, Order.items)

          session.query(User).join(
              (Order, User.orders),
              (Item, Item.order_id == Order.id)
          )

          session.query(User).join(Order, Item)

          # ... and several more forms actually

      Why it’s legacy: being able to chain multiple ON clauses in one call to `Query.join()` is yet another attempt to solve the problem of being able to specify what entity to join from, and is the source of a large variety of potential calling patterns that are internally expensive and complicated to parse and accommodate.

      Modern calling pattern: Use relationship-bound attributes or SQL-oriented ON clauses within separate calls, so that each call to `Query.join()` knows what the left side should be:

          session.query(User).join(User.orders).join(
              Item, Item.order_id == Order.id)

    Parameters

      - *props – Incoming arguments for `Query.join()`, the props collection in modern use should be considered to be a one or two argument form, either as a single “target” entity or ORM attribute-bound relationship, or as a target entity plus an “on clause” which may be a SQL expression or ORM attribute-bound relationship.

      - isouter=False – If True, the join used will be a left outer join, just as if the `Query.outerjoin()` method were called.

      - full=False –

        render FULL OUTER JOIN; implies `isouter`.

        New in version 1.1.

      - from_joinpoint=False –

        When using `aliased=True`, a setting of True here will cause the join to be from the most recent joined target, rather than starting back from the original FROM clauses of the query.

        Note

        This flag is considered legacy.

      - aliased=False –

        If True, indicate that the JOIN target should be anonymously aliased. Subsequent calls to `Query.filter()` and similar will adapt the incoming criterion to the target alias, until `Query.reset_joinpoint()` is called.

        Note

        This flag is considered legacy.

    See also

    Querying with Joins in the ORM tutorial.

    Mapping Class Inheritance Hierarchies for details on how `Query.join()` is used for inheritance relationships.

    `join()` - a standalone ORM-level join function, used internally by `Query.join()`, which in previous SQLAlchemy versions was the primary ORM-level joining interface.

  method `sqlalchemy.orm.Query.`label(name)

    Return the full SELECT statement represented by this `Query`, converted to a scalar subquery with a label of the given name.

    Analogous to `SelectBase.label()`.

  attribute `sqlalchemy.orm.Query.`lazy_loaded_from

    An `InstanceState` that is using this `Query` for a lazy load operation.

    Deprecated since version 1.4: This attribute should be viewed via the `ORMExecuteState.lazy_loaded_from` attribute, within the context of the `SessionEvents.do_orm_execute()` event.

    See also

    `ORMExecuteState.lazy_loaded_from`

  method `sqlalchemy.orm.Query.`limit(limit)

    Apply a `LIMIT` to the query and return the newly resulting `Query`.

  method `sqlalchemy.orm.Query.`merge_result(iterator, load=True)

    Merge a result into this `Query` object’s Session.

    Deprecated since version 1.4: The `Query.merge_result()` method is considered legacy as of the 1.x series of SQLAlchemy and becomes a legacy construct in 2.0. The method is superseded by the `merge_frozen_result()` function. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)

    Given an iterator returned by a `Query` of the same structure as this one, return an identical iterator of results, with all mapped instances merged into the session using `Session.merge()`. This is an optimized method which will merge all mapped instances, preserving the structure of the result rows and unmapped columns with less method overhead than that of calling `Session.merge()` explicitly for each value.

    The structure of the results is determined based on the column list of this `Query` - if these do not correspond, unchecked errors will occur.

    The ‘load’ argument is the same as that of `Session.merge()`.

    For an example of how `Query.merge_result()` is used, see the source code for the example Dogpile Caching, where `Query.merge_result()` is used to efficiently restore state from a cache back into a target `Session`.

  method `sqlalchemy.orm.Query.`offset(offset)

    Apply an `OFFSET` to the query and return the newly resulting `Query`.

  method `sqlalchemy.orm.Query.`one()

    Return exactly one result or raise an exception.

    Raises `sqlalchemy.orm.exc.NoResultFound` if the query selects no rows. Raises `sqlalchemy.orm.exc.MultipleResultsFound` if multiple object identities are returned, or if multiple rows are returned for a query that returns only scalar values as opposed to full identity-mapped entities.

    Calling `one()` results in an execution of the underlying query.

    See also

    `Query.first()`

    `Query.one_or_none()`

  method `sqlalchemy.orm.Query.`one_or_none()

    Return at most one result or raise an exception.

    Returns `None` if the query selects no rows. Raises `sqlalchemy.orm.exc.MultipleResultsFound` if multiple object identities are returned, or if multiple rows are returned for a query that returns only scalar values as opposed to full identity-mapped entities.

    Calling `Query.one_or_none()` results in an execution of the underlying query.

    New in version 1.0.9: Added `Query.one_or_none()`

    See also

    `Query.first()`

    `Query.one()`

  method `sqlalchemy.orm.Query.`only_return_tuples(value)

    When set to True, the query results will always be a tuple.

    This is specifically for single element queries. The default is False.

    New in version 1.2.5.

    See also

    `Query.is_single_entity()`

  method `sqlalchemy.orm.Query.`options(*args)

    Return a new `Query` object, applying the given list of mapper options.

    Most supplied options regard changing how column- and relationship-mapped attributes are loaded.

    See also

    Deferred Column Loader Query Options

    Relationship Loading with Loader Options

  method `sqlalchemy.orm.Query.`order_by(*clauses)

    Apply one or more ORDER BY criteria to the query and return the newly resulting `Query`.

    e.g.:

        q = session.query(Entity).order_by(Entity.id, Entity.name)

    All existing ORDER BY criteria may be cancelled by passing `None` by itself. New ORDER BY criteria may then be added by invoking `Query.order_by()` again, e.g.:

        # will erase all ORDER BY and ORDER BY new_col alone
        q = q.order_by(None).order_by(new_col)

    See also

    These sections describe ORDER BY in terms of 2.0 style invocation but apply to `Query` as well:

    ORDER BY - in the SQLAlchemy 1.4 / 2.0 Tutorial

    Ordering or Grouping by a Label - in the SQLAlchemy 1.4 / 2.0 Tutorial

  method `sqlalchemy.orm.Query.`outerjoin(target, *props, **kwargs)

    Create a left outer join against this `Query` object’s criterion and apply generatively, returning the newly resulting `Query`.

    Usage is the same as the `join()` method.

  method `sqlalchemy.orm.Query.`params(*args, **kwargs)

    Add values for bind parameters which may have been specified in filter().

    Parameters may be specified using **kwargs, or optionally a single dictionary as the first positional argument. The reason for both is that **kwargs is convenient, however some parameter dictionaries contain unicode keys in which case **kwargs cannot be used.

  method `sqlalchemy.orm.Query.`populate_existing()

    Return a `Query` that will expire and refresh all instances as they are loaded, or reused from the current `Session`.

    As of SQLAlchemy 1.4, the `Query.populate_existing()` method is equivalent to using the `populate_existing` execution option at the ORM level. See the section Populate Existing for further background on this option.

  method `sqlalchemy.orm.Query.`reset_joinpoint()

    Return a new `Query`, where the “join point” has been reset back to the base FROM entities of the query.

    This method is usually used in conjunction with the `aliased=True` feature of the `Query.join()` method. See the example in `Query.join()` for how this is used.

  method `sqlalchemy.orm.Query.`scalar()

    Return the first element of the first result or None if no rows present. If multiple rows are returned, raises MultipleResultsFound.

        >>> session.query(Item).scalar()
        <Item>
        >>> session.query(Item.id).scalar()
        1
        >>> session.query(Item.id).filter(Item.id < 0).scalar()
        None
        >>> session.query(Item.id, Item.name).scalar()
        1
        >>> session.query(func.count(Parent.id)).scalar()
        20

    This results in an execution of the underlying query.

  method `sqlalchemy.orm.Query.`scalar_subquery()

    Return the full SELECT statement represented by this `Query`, converted to a scalar subquery.

    Analogous to `SelectBase.scalar_subquery()`.

    Changed in version 1.4: The `Query.scalar_subquery()` method replaces the `Query.as_scalar()` method.

  method `sqlalchemy.orm.Query.`select_entity_from(from_obj)

    Set the FROM clause of this `Query` to a core selectable, applying it as a replacement FROM clause for corresponding mapped entities.

    Deprecated since version 1.4: The `Query.select_entity_from()` method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Use the `aliased()` construct instead (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)

    The `Query.select_entity_from()` method supplies an alternative approach to the use case of applying an `aliased()` construct explicitly throughout a query. Instead of referring to the `aliased()` construct explicitly, `Query.select_entity_from()` automatically adapts all occurrences of the entity to the target selectable.

    Given a case for `aliased()` such as selecting `User` objects from a SELECT statement:

        select_stmt = select(User).where(User.id == 7)
        user_alias = aliased(User, select_stmt)

        q = session.query(user_alias).\
            filter(user_alias.name == 'ed')

    Above, we apply the `user_alias` object explicitly throughout the query. When it’s not feasible for `user_alias` to be referenced explicitly in many places, `Query.select_entity_from()` may be used at the start of the query to adapt the existing `User` entity:

        q = session.query(User).\
            select_entity_from(select_stmt.subquery()).\
            filter(User.name == 'ed')

    Above, the generated SQL will show that the `User` entity is adapted to our statement, even in the case of the WHERE clause:

        SELECT anon_1.id AS anon_1_id, anon_1.name AS anon_1_name
        FROM (SELECT "user".id AS id, "user".name AS name
        FROM "user"
        WHERE "user".id = :id_1) AS anon_1
        WHERE anon_1.name = :name_1

    The `Query.select_entity_from()` method is similar to the `Query.select_from()` method, in that it sets the FROM clause of the query. The difference is that it additionally applies adaptation to the other parts of the query that refer to the primary entity. If above we had used `Query.select_from()` instead, the SQL generated would have been:

        -- uses plain select_from(), not select_entity_from()
        SELECT "user".id AS user_id, "user".name AS user_name
        FROM "user", (SELECT "user".id AS id, "user".name AS name
        FROM "user"
        WHERE "user".id = :id_1) AS anon_1
        WHERE "user".name = :name_1

    To supply textual SQL to the `Query.select_entity_from()` method, we can make use of the `text()` construct. However, the `text()` construct needs to be aligned with the columns of our entity, which is achieved by making use of the `TextClause.columns()` method:

        text_stmt = text("select id, name from user").columns(
            User.id, User.name).subquery()
        q = session.query(User).select_entity_from(text_stmt)

    `Query.select_entity_from()` itself accepts an `aliased()` object, so that the special options of `aliased()` such as `aliased.adapt_on_names` may be used within the scope of the `Query.select_entity_from()` method’s adaptation services. Suppose a view `user_view` also returns rows from `user`. If we reflect this view into a `Table`, this view has no relationship to the `Table` to which we are mapped, however we can use name matching to select from it:

        user_view = Table('user_view', metadata,
                          autoload_with=engine)
        user_view_alias = aliased(
            User, user_view, adapt_on_names=True)
        q = session.query(User).\
            select_entity_from(user_view_alias).\
            order_by(User.name)

    Changed in version 1.1.7: The `Query.select_entity_from()` method now accepts an `aliased()` object as an alternative to a `FromClause` object.

    Parameters

      from_obj – a `FromClause` object that will replace the FROM clause of this `Query`. It also may be an instance of `aliased()`.

    See also

    `Query.select_from()`

  method `sqlalchemy.orm.Query.`select_from(*from_obj)

    Set the FROM clause of this `Query` explicitly.

    `Query.select_from()` is often used in conjunction with `Query.join()` in order to control which entity is selected from on the “left” side of the join.

    The entity or selectable object here effectively replaces the “left edge” of any calls to `Query.join()`, when no joinpoint is otherwise established - usually, the default “join point” is the leftmost entity in the `Query` object’s list of entities to be selected.

    A typical example:

        q = session.query(Address).select_from(User).\
            join(User.addresses).\
            filter(User.name == 'ed')

    Which produces SQL equivalent to:

        SELECT address.* FROM user
        JOIN address ON user.id=address.user_id
        WHERE user.name = :name_1

    Parameters

      *from_obj – collection of one or more entities to apply to the FROM clause. Entities can be mapped classes, `AliasedClass` objects, `Mapper` objects as well as core `FromClause` elements like subqueries.

    Changed in version 0.9: This method no longer applies the given FROM object to be the selectable from which matching entities select from; the `select_entity_from()` method now accomplishes this. See that method for a description of this behavior.

    See also

    `Query.join()`

    `Query.select_entity_from()`

  attribute `sqlalchemy.orm.Query.`selectable

    Return the `Select` object emitted by this `Query`.

    Used for `inspect()` compatibility, this is equivalent to:

        query.enable_eagerloads(False).with_labels().statement

  method `sqlalchemy.orm.Query.`set_label_style(style)

    Apply column labels to the return value of Query.statement.

    Indicates that this Query’s statement accessor should return a SELECT statement that applies labels to all columns in the form <tablename>_<columnname>; this is commonly used to disambiguate columns from multiple tables which have the same name.

    When the Query actually issues SQL to load rows, it always uses column labeling.

    Note

    The `Query.set_label_style()` method only applies the output of `Query.statement`, and not to any of the result-row invoking systems of `Query` itself, e.g. `Query.first()`, `Query.all()`, etc. To execute a query using `Query.set_label_style()`, invoke the `Query.statement` using `Session.execute()`:

        result = session.execute(
            query
            .set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
            .statement
        )

    New in version 1.4.

  method `sqlalchemy.orm.Query.`slice(start, stop)

    Computes the “slice” of the `Query` represented by the given indices and returns the resulting `Query`.

    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,

        session.query(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)

    See also

    `Query.limit()`

    `Query.offset()`

  attribute `sqlalchemy.orm.Query.`statement

    The full SELECT statement represented by this Query.

    The statement by default will not have disambiguating labels applied to the construct unless with_labels(True) is called first.

  method `sqlalchemy.orm.Query.`subquery(name=None, with_labels=False, reduce_columns=False)

    Return the full SELECT statement represented by this `Query`, embedded within an `Alias`.

    Eager JOIN generation within the query is disabled.

    Parameters

      - name – string name to be assigned as the alias; this is passed through to `FromClause.alias()`. If `None`, a name will be deterministically generated at compile time.

      - with_labels – if True, `with_labels()` will be called on the `Query` first to apply table-qualified labels to all columns.

      - reduce_columns – if True, `Select.reduce_columns()` will be called on the resulting `select()` construct, to remove same-named columns where one also refers to the other via foreign key or WHERE clause equivalence.

  method `sqlalchemy.orm.Query.`union(*q)

    Produce a UNION of this Query against one or more queries.

    e.g.:

        q1 = sess.query(SomeClass).filter(SomeClass.foo=='bar')
        q2 = sess.query(SomeClass).filter(SomeClass.bar=='foo')

        q3 = q1.union(q2)

    The method accepts multiple Query objects so as to control the level of nesting. A series of `union()` calls such as:

        x.union(y).union(z).all()

    will nest on each `union()`, and produces:

        SELECT * FROM (SELECT * FROM (SELECT * FROM X UNION
                        SELECT * FROM y) UNION SELECT * FROM Z)

    Whereas:

        x.union(y, z).all()

    produces:

        SELECT * FROM (SELECT * FROM X UNION SELECT * FROM y UNION
                        SELECT * FROM Z)

    Note that many database backends do not allow ORDER BY to be rendered on a query called within UNION, EXCEPT, etc. To disable all ORDER BY clauses including those configured on mappers, issue `query.order_by(None)` - the resulting `Query` object will not render ORDER BY within its SELECT statement.

  method `sqlalchemy.orm.Query.`union_all(*q)

    Produce a UNION ALL of this Query against one or more queries.

    Works the same way as `Query.union()`. See that method for usage examples.

  method `sqlalchemy.orm.Query.`update(values, synchronize_session='evaluate', update_args=None)

    Perform an UPDATE with an arbitrary WHERE clause.

    Updates rows matched by this query in the database.

    E.g.:

        sess.query(User).filter(User.age == 25).\
            update({User.age: User.age - 10}, synchronize_session=False)

        sess.query(User).filter(User.age == 25).\
            update({"age": User.age - 10}, synchronize_session='evaluate')

    Warning

    See the section UPDATE and DELETE with arbitrary WHERE clause for important caveats and warnings, including limitations when using arbitrary UPDATE and DELETE with mapper inheritance configurations.

    Parameters

      - values – a dictionary with attributes names, or alternatively mapped attributes or SQL expressions, as keys, and literal values or sql expressions as values. If parameter-ordered mode is desired, the values can be passed as a list of 2-tuples; this requires that the `update.preserve_parameter_order` flag is passed to the `Query.update.update_args` dictionary as well.

      - synchronize_session – chooses the strategy to update the attributes on objects in the session. See the section UPDATE and DELETE with arbitrary WHERE clause for a discussion of these strategies.

      - update_args – Optional dictionary, if present will be passed to the underlying `update()` construct as the `**kw` for the object. May be used to pass dialect-specific arguments such as `mysql_limit`, as well as other special arguments such as `update.preserve_parameter_order`.

    Returns

      the count of rows matched as returned by the database’s “row count” feature.

    See also

    UPDATE and DELETE with arbitrary WHERE clause

  method `sqlalchemy.orm.Query.`value(column)

    Return a scalar result corresponding to the given column expression.

    Deprecated since version 1.4: `Query.value()` is deprecated and will be removed in a future release. Please use `Query.with_entities()` in combination with `Query.scalar()`

  method `sqlalchemy.orm.Query.`values(*columns)

    Return an iterator yielding result tuples corresponding to the given list of columns

    Deprecated since version 1.4: `Query.values()` is deprecated and will be removed in a future release. Please use `Query.with_entities()`

  method `sqlalchemy.orm.Query.`where(*criterion)

    A synonym for `Query.filter()`.

    New in version 1.4.

  attribute `sqlalchemy.orm.Query.`whereclause

    A readonly attribute which returns the current WHERE criterion for this Query.

    This returned value is a SQL expression construct, or `None` if no criterion has been established.

  method `sqlalchemy.orm.Query.`with_entities(*entities)

    Return a new `Query` replacing the SELECT list with the given entities.

    e.g.:

        # Users, filtered on some arbitrary criterion
        # and then ordered by related email address
        q = session.query(User).\
                    join(User.address).\
                    filter(User.name.like('%ed%')).\
                    order_by(Address.email)

        # given *only* User.id==5, Address.email, and 'q', what
        # would the *next* User in the result be ?
        subq = q.with_entities(Address.email).\
                    order_by(None).\
                    filter(User.id==5).\
                    subquery()
        q = q.join((subq, subq.c.email < Address.email)).\
                    limit(1)

  method `sqlalchemy.orm.Query.`with_for_update(read=False, nowait=False, of=None, skip_locked=False, key_share=False)

    return a new `Query` with the specified options for the `FOR UPDATE` clause.

    The behavior of this method is identical to that of `GenerativeSelect.with_for_update()`. When called with no arguments, the resulting `SELECT` statement will have a `FOR UPDATE` clause appended. When additional arguments are specified, backend-specific options such as `FOR UPDATE NOWAIT` or `LOCK IN SHARE MODE` can take effect.

    E.g.:

        q = sess.query(User).populate_existing().with_for_update(nowait=True, of=User)

    The above query on a PostgreSQL backend will render like:

        SELECT users.id AS users_id FROM users FOR UPDATE OF users NOWAIT

    Warning

    Using `with_for_update` in the context of eager loading relationships is not officially supported or recommended by SQLAlchemy and may not work with certain queries on various database backends. When `with_for_update` is successfully used with a query that involves `joinedload()`, SQLAlchemy will attempt to emit SQL that locks all involved tables.

    Note

    It is generally a good idea to combine the use of the `Query.populate_existing()` method when using the `Query.with_for_update()` method. The purpose of `Query.populate_existing()` is to force all the data read from the SELECT to be populated into the ORM objects returned, even if these objects are already in the identity map.

    See also

    `GenerativeSelect.with_for_update()` - Core level method with full argument and behavioral description.

    `Query.populate_existing()` - overwrites attributes of objects already loaded in the identity map.

  method `sqlalchemy.orm.Query.`with_labels()

    Deprecated since version 1.4: The `Query.with_labels()` and `Query.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)

  method `sqlalchemy.orm.Query.`with_parent(instance, property=None, from_entity=None)

    Add filtering criterion that relates the given instance to a child object or collection, using its attribute state as well as an established `relationship()` configuration.

    Deprecated since version 1.4: The `Query.with_parent()` method is considered legacy as of the 1.x series of SQLAlchemy and becomes a legacy construct in 2.0. Use the `with_parent()` standalone construct. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)

    The method uses the `with_parent()` function to generate the clause, the result of which is passed to `Query.filter()`.

    Parameters are the same as `with_parent()`, with the exception that the given property can be None, in which case a search is performed against this `Query` object’s target mapper.

    Parameters

      - instance – An instance which has some `relationship()`.

      - property – String property name, or class-bound attribute, which indicates what relationship from the instance should be used to reconcile the parent/child relationship.

      - from_entity – Entity in which to consider as the left side. This defaults to the “zero” entity of the `Query` itself.

  method `sqlalchemy.orm.Query.`with_polymorphic(cls_or_mappers, selectable=None, polymorphic_on=None)

    Load columns for inheriting classes.

    Deprecated since version 1.4: The `Query.with_polymorphic()` method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. Use the orm.with_polymorphic() standalone function (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)

    This is a legacy method which is replaced by the `with_polymorphic()` function.

    Warning

    The `Query.with_polymorphic()` method does not support 1.4/2.0 style features including `with_loader_criteria()`. Please migrate code to use `with_polymorphic()`.

    `Query.with_polymorphic()` applies transformations to the “main” mapped class represented by this `Query`. The “main” mapped class here means the `Query` object’s first argument is a full class, i.e. `session.query(SomeClass)`. These transformations allow additional tables to be present in the FROM clause so that columns for a joined-inheritance subclass are available in the query, both for the purposes of load-time efficiency as well as the ability to use these columns at query time.

    See also

    Using with_polymorphic - illustrates current patterns

  method `sqlalchemy.orm.Query.`with_session(session)

    Return a `Query` that will use the given `Session`.

    While the `Query` object is normally instantiated using the `Session.query()` method, it is legal to build the `Query` directly without necessarily using a `Session`. Such a `Query` object, or any `Query` already associated with a different `Session`, can produce a new `Query` object associated with a target session using this method:

        from sqlalchemy.orm import Query

        query = Query([MyClass]).filter(MyClass.id == 5)

        result = query.with_session(my_session).one()

  method `sqlalchemy.orm.Query.`with_transformation(fn)

    Return a new `Query` object transformed by the given function.

    E.g.:

        def filter_something(criterion):
            def transform(q):
                return q.filter(criterion)
            return transform

        q = q.with_transformation(filter_something(x==5))

    This allows ad-hoc recipes to be created for `Query` objects. See the example at Building Transformers.

  method `sqlalchemy.orm.Query.`yield_per(count)

    Yield only `count` rows at a time.

    The purpose of this method is when fetching very large result sets (> 10K rows), to batch results in sub-collections and yield them out partially, so that the Python interpreter doesn’t need to declare very large areas of memory which is both time consuming and leads to excessive memory use. The performance from fetching hundreds of thousands of rows can often double when a suitable yield-per setting (e.g. approximately 1000) is used, even with DBAPIs that buffer rows (which are most).

    As of SQLAlchemy 1.4, the `Query.yield_per()` method is equivalent to using the `yield_per` execution option at the ORM level. See the section Yield Per for further background on this option.

## ORM-Specific Query Constructs

Object Name | Description
--- | ---
aliased(element[, alias, name, flat, ...]) | Produce an alias of the given element, usually an `AliasedClass` instance.
AliasedClass | Represents an “aliased” form of a mapped class for usage with Query.
AliasedInsp | Provide an inspection interface for an `AliasedClass` object.
Bundle | A grouping of SQL expressions that are returned by a `Query` under one namespace.
join(left, right[, onclause, isouter, ...]) | Produce an inner join between left and right clauses.
outerjoin(left, right[, onclause, full, ...]) | Produce a left outer join between left and right clauses.
with_loader_criteria(entity_or_base, where_criteria[, loader_only, include_aliases, ...]) | Add additional WHERE criteria to the load for all occurrences of a particular entity.
with_parent(instance, prop[, from_entity]) | Create filtering criterion that relates this query’s primary entity to the given related instance, using established `relationship()` configuration.

function sqlalchemy.orm.aliased(element, alias=None, name=None, flat=False, adapt_on_names=False)

  Produce an alias of the given element, usually an `AliasedClass` instance.

  E.g.:

      my_alias = aliased(MyClass)

      session.query(MyClass, my_alias).filter(MyClass.id > my_alias.id)

  The `aliased()` function is used to create an ad-hoc mapping of a mapped class to a new selectable. By default, a selectable is generated from the normally mapped selectable (typically a `Table` ) using the `FromClause.alias()` method. However, `aliased()` can also be used to link the class to a new `select()` statement. Also, the `with_polymorphic()` function is a variant of `aliased()` that is intended to specify a so-called “polymorphic selectable”, that corresponds to the union of several joined-inheritance subclasses at once.

  For convenience, the `aliased()` function also accepts plain `FromClause` constructs, such as a `Table` or `select()` construct. In those cases, the `FromClause.alias()` method is called on the object and the new `Alias` object returned. The returned `Alias` is not ORM-mapped in this case.

  See also

  ORM Entity Aliases - in the SQLAlchemy 1.4 / 2.0 Tutorial

  Selecting ORM Aliases - in the ORM Querying Guide

  Parameters

    - element – element to be aliased. Is normally a mapped class, but for convenience can also be a `FromClause` element.

    - alias – Optional selectable unit to map the element to. This is usually used to link the object to a subquery, and should be an aliased select construct as one would produce from the `Query.subquery()` method or the `Select.subquery()` or `Select.alias()` methods of the `select()` construct.

    - name – optional string name to use for the alias, if not specified by the `alias` parameter. The name, among other things, forms the attribute name that will be accessible via tuples returned by a `Query` object. Not supported when creating aliases of `Join` objects.

    - flat – Boolean, will be passed through to the `FromClause.alias()` call so that aliases of `Join` objects will alias the individual tables inside the join, rather than creating a subquery. This is generally supported by all modern databases with regards to right-nested joins and generally produces more efficient queries.

    - adapt_on_names –

      if True, more liberal “matching” will be used when mapping the mapped columns of the ORM entity to those of the given selectable - a name-based match will be performed if the given selectable doesn’t otherwise have a column that corresponds to one on the entity. The use case for this is when associating an entity with some derived selectable such as one that uses aggregate functions:

          class UnitPrice(Base):
              __tablename__ = 'unit_price'
              ...
              unit_id = Column(Integer)
              price = Column(Numeric)

          aggregated_unit_price = Session.query(
                                      func.sum(UnitPrice.price).label('price')
                                  ).group_by(UnitPrice.unit_id).subquery()

          aggregated_unit_price = aliased(UnitPrice,
                      alias=aggregated_unit_price, adapt_on_names=True)

      Above, functions on `aggregated_unit_price` which refer to `.price` will return the `func.sum(UnitPrice.price).label('price')` column, as it is matched on the name “price”. Ordinarily, the “price” function wouldn’t have any “column correspondence” to the actual `UnitPrice.price` column as it is not a proxy of the original.

class sqlalchemy.orm.util.AliasedClass(mapped_class_or_ac, alias=None, name=None, flat=False, adapt_on_names=False, with_polymorphic_mappers=(), with_polymorphic_discriminator=None, base_alias=None, use_mapper_path=False, represents_outer_join=False)

  Represents an “aliased” form of a mapped class for usage with Query.

  The ORM equivalent of a `alias()` construct, this object mimics the mapped class using a `__getattr__` scheme and maintains a reference to a real `Alias` object.

  A primary purpose of `AliasedClass` is to serve as an alternate within a SQL statement generated by the ORM, such that an existing mapped entity can be used in multiple contexts. A simple example:

      # find all pairs of users with the same name
      user_alias = aliased(User)
      session.query(User, user_alias).\
                      join((user_alias, User.id > user_alias.id)).\
                      filter(User.name == user_alias.name)

  `AliasedClass` is also capable of mapping an existing mapped class to an entirely new selectable, provided this selectable is column- compatible with the existing mapped selectable, and it can also be configured in a mapping as the target of a `relationship()`. See the links below for examples.

  The `AliasedClass` object is constructed typically using the `aliased()` function. It also is produced with additional configuration when using the `with_polymorphic()` function.

  The resulting object is an instance of `AliasedClass`. This object implements an attribute scheme which produces the same attribute and method interface as the original mapped class, allowing `AliasedClass` to be compatible with any attribute technique which works on the original class, including hybrid attributes (see Hybrid Attributes).

  The `AliasedClass` can be inspected for its underlying `Mapper`, aliased selectable, and other information using `inspect()`:

      from sqlalchemy import inspect
      my_alias = aliased(MyClass)
      insp = inspect(my_alias)

  The resulting inspection object is an instance of `AliasedInsp`.

  See also

  `aliased()`

  `with_polymorphic()`

  Relationship to Aliased Class

  Row-Limited Relationships with Window Functions

class sqlalchemy.orm.util.AliasedInsp(entity, inspected, selectable, name, with_polymorphic_mappers, polymorphic_on, _base_alias, _use_mapper_path, adapt_on_names, represents_outer_join, nest_adapters)

  Provide an inspection interface for an `AliasedClass` object.

  The `AliasedInsp` object is returned given an `AliasedClass` using the `inspect()` function:

      from sqlalchemy import inspect
      from sqlalchemy.orm import aliased

      my_alias = aliased(MyMappedClass)
      insp = inspect(my_alias)

  Attributes on `AliasedInsp` include:

  - `entity` - the `AliasedClass` represented.

  - `mapper` - the `Mapper` mapping the underlying class.

  - `selectable` - the `Alias` construct which ultimately represents an aliased `Table` or `Select` construct.

  - `name` - the name of the alias. Also is used as the attribute name when returned in a result tuple from `Query`.

  - `with_polymorphic_mappers` - collection of `Mapper` objects indicating all those mappers expressed in the select construct for the `AliasedClass`.

  - `polymorphic_on` - an alternate column or SQL expression which will be used as the “discriminator” for a polymorphic load.

  See also

  Runtime Inspection API

  Class signature

  class `sqlalchemy.orm.AliasedInsp` (`sqlalchemy.orm.ORMEntityColumnsClauseRole`, `sqlalchemy.orm.ORMFromClauseRole`, `sqlalchemy.sql.traversals.MemoizedHasCacheKey`, `sqlalchemy.orm.base.InspectionAttr`)

class sqlalchemy.orm.Bundle(name, *exprs, **kw)

  A grouping of SQL expressions that are returned by a `Query` under one namespace.

  The `Bundle` essentially allows nesting of the tuple-based results returned by a column-oriented `Query` object. It also is extensible via simple subclassing, where the primary capability to override is that of how the set of expressions should be returned, allowing post-processing as well as custom return types, without involving ORM identity-mapped classes.

  New in version 0.9.0.

  See also

  Column Bundles

  Class signature

  class `sqlalchemy.orm.Bundle` (`sqlalchemy.orm.ORMColumnsClauseRole`, `sqlalchemy.sql.annotation.SupportsCloneAnnotations`, `sqlalchemy.sql.traversals.MemoizedHasCacheKey`, `sqlalchemy.orm.base.InspectionAttr`)

  method `sqlalchemy.orm.Bundle.`__init__(name, *exprs, **kw)

    Construct a new `Bundle`.

    e.g.:

        bn = Bundle("mybundle", MyClass.x, MyClass.y)

        for row in session.query(bn).filter(
                bn.c.x == 5).filter(bn.c.y == 4):
            print(row.mybundle.x, row.mybundle.y)

    Parameters

      - name – name of the bundle.

      - *exprs – columns or SQL expressions comprising the bundle.

      - single_entity=False – if True, rows for this `Bundle` can be returned as a “single entity” outside of any enclosing tuple in the same manner as a mapped entity.

  attribute `sqlalchemy.orm.Bundle.`c = None

    An alias for `Bundle.columns`.

  attribute `sqlalchemy.orm.Bundle.`columns = None

    A namespace of SQL expressions referred to by this `Bundle`.

    > e.g.:

    >     bn = Bundle("mybundle", MyClass.x, MyClass.y)

    >     q = sess.query(bn).filter(bn.c.x == 5)

    > Nesting of bundles is also supported:

    >     b1 = Bundle("b1",
    >             Bundle('b2', MyClass.a, MyClass.b),
    >             Bundle('b3', MyClass.x, MyClass.y)
    >         )

    >     q = sess.query(b1).filter(
    >         b1.c.b2.c.a == 5).filter(b1.c.b3.c.y == 9)

    See also

    `Bundle.c`

  method `sqlalchemy.orm.Bundle.`create_row_processor(query, procs, labels)

    Produce the “row processing” function for this `Bundle`.

    May be overridden by subclasses.

    See also

    Column Bundles - includes an example of subclassing.

  attribute `sqlalchemy.orm.Bundle.`is_aliased_class = False

    True if this object is an instance of `AliasedClass`.

  attribute `sqlalchemy.orm.Bundle.`is_bundle = True

    True if this object is an instance of `Bundle`.

  attribute `sqlalchemy.orm.Bundle.`is_clause_element = False

    True if this object is an instance of `ClauseElement`.

  attribute `sqlalchemy.orm.Bundle.`is_mapper = False

    True if this object is an instance of `Mapper`.

  method `sqlalchemy.orm.Bundle.`label(name)

    Provide a copy of this `Bundle` passing a new label.

  attribute `sqlalchemy.orm.Bundle.`single_entity = False

    If True, queries for a single Bundle will be returned as a single entity, rather than an element within a keyed tuple.

class sqlalchemy.orm.Load(entity)

  Represents loader options which modify the state of a `Query` in order to affect how various mapped attributes are loaded.

  The `Load` object is in most cases used implicitly behind the scenes when one makes use of a query option like `joinedload()`, `defer()`, or similar. However, the `Load` object can also be used directly, and in some cases can be useful.

  To use `Load` directly, instantiate it with the target mapped class as the argument. This style of usage is useful when dealing with a `Query` that has multiple entities:

      myopt = Load(MyClass).joinedload("widgets")

  The above `myopt` can now be used with `Query.options()`, where it will only take effect for the `MyClass` entity:

      session.query(MyClass, MyOtherClass).options(myopt)

  One case where `Load` is useful as public API is when specifying “wildcard” options that only take effect for a certain class:

      session.query(Order).options(Load(Order).lazyload('*'))

  Above, all relationships on `Order` will be lazy-loaded, but other attributes on those descendant objects will load using their normal loader strategy.

  See also

  Deferred Column Loader Query Options

  Deferred Loading across Multiple Entities

  Relationship Loading with Loader Options

  Class signature

  class `sqlalchemy.orm.Load` (`sqlalchemy.sql.expression.Generative`, `sqlalchemy.orm.LoaderOption`)

  method `sqlalchemy.orm.Load.`contains_eager(attr, alias=None)

    Produce a new `Load` object with the `contains_eager()` option applied.

    See `contains_eager()` for usage examples.

  method `sqlalchemy.orm.Load.`defaultload(attr)

    Produce a new `Load` object with the `defaultload()` option applied.

    See `defaultload()` for usage examples.

  method `sqlalchemy.orm.Load.`defer(key, raiseload=False)

    Produce a new `Load` object with the `defer()` option applied.

    See `defer()` for usage examples.

  method `sqlalchemy.orm.Load.`immediateload(attr)

    Produce a new `Load` object with the `immediateload()` option applied.

    See `immediateload()` for usage examples.

  method `sqlalchemy.orm.Load.`joinedload(attr, innerjoin=None)

    Produce a new `Load` object with the `joinedload()` option applied.

    See `joinedload()` for usage examples.

  method `sqlalchemy.orm.Load.`lazyload(attr)

    Produce a new `Load` object with the `lazyload()` option applied.

    See `lazyload()` for usage examples.

  method `sqlalchemy.orm.Load.`load_only(*attrs)

    Produce a new `Load` object with the `load_only()` option applied.

    See `load_only()` for usage examples.

  method `sqlalchemy.orm.Load.`noload(attr)

    Produce a new `Load` object with the `noload()` option applied.

    See `noload()` for usage examples.

  method `sqlalchemy.orm.Load.`options(*opts)

    Apply a series of options as sub-options to this `Load` object.

    E.g.:

        query = session.query(Author)
        query = query.options(
                    joinedload(Author.book).options(
                        load_only(Book.summary, Book.excerpt),
                        joinedload(Book.citations).options(
                            joinedload(Citation.author)
                        )
                    )
                )

    Parameters

      *opts – A series of loader option objects (ultimately `Load` objects) which should be applied to the path specified by this `Load` object.

    New in version 1.3.6.

    See also

    `defaultload()`

    Relationship Loading with Loader Options

    Deferred Loading across Multiple Entities

  method `sqlalchemy.orm.Load.`process_compile_state(compile_state)

    Apply a modification to a given `CompileState`.

  method `sqlalchemy.orm.Load.`process_compile_state_replaced_entities(compile_state, mapper_entities)

    Apply a modification to a given `CompileState`, given entities that were replaced by with_only_columns() or with_entities().

    New in version 1.4.19.

  attribute `sqlalchemy.orm.Load.`propagate_to_loaders = False

    if True, indicate this option should be carried along to “secondary” SELECT statements that occur for relationship lazy loaders as well as attribute load / refresh operations.

  method `sqlalchemy.orm.Load.`raiseload(attr, sql_only=False)

    Produce a new `Load` object with the `raiseload()` option applied.

    See `raiseload()` for usage examples.

  method `sqlalchemy.orm.Load.`selectin_polymorphic(classes)

    Produce a new `Load` object with the `selectin_polymorphic()` option applied.

    See `selectin_polymorphic()` for usage examples.

  method `sqlalchemy.orm.Load.`selectinload(attr)

    Produce a new `Load` object with the `selectinload()` option applied.

    See `selectinload()` for usage examples.

  method `sqlalchemy.orm.Load.`subqueryload(attr)

    Produce a new `Load` object with the `subqueryload()` option applied.

    See `subqueryload()` for usage examples.

  method `sqlalchemy.orm.Load.`undefer(key)

    Produce a new `Load` object with the `undefer()` option applied.

    See `undefer()` for usage examples.

  method `sqlalchemy.orm.Load.`undefer_group(name)

    Produce a new `Load` object with the `undefer_group()` option applied.

    See `undefer_group()` for usage examples.

  method `sqlalchemy.orm.Load.`with_expression(key, expression)

    Produce a new `Load` object with the `with_expression()` option applied.

    See `with_expression()` for usage examples.

function sqlalchemy.orm.with_loader_criteria(entity_or_base, where_criteria, loader_only=False, include_aliases=False, propagate_to_loaders=True, track_closure_variables=True)

  Add additional WHERE criteria to the load for all occurrences of a particular entity.

  New in version 1.4.

  The `with_loader_criteria()` option is intended to add limiting criteria to a particular kind of entity in a query, globally, meaning it will apply to the entity as it appears in the SELECT query as well as within any subqueries, join conditions, and relationship loads, including both eager and lazy loaders, without the need for it to be specified in any particular part of the query. The rendering logic uses the same system used by single table inheritance to ensure a certain discriminator is applied to a table.

  E.g., using 2.0-style queries, we can limit the way the `User.addresses` collection is loaded, regardless of the kind of loading used:

      from sqlalchemy.orm import with_loader_criteria

      stmt = select(User).options(
          selectinload(User.addresses),
          with_loader_criteria(Address, Address.email_address != 'foo'))
      )

  Above, the “selectinload” for `User.addresses` will apply the given filtering criteria to the WHERE clause.

  Another example, where the filtering will be applied to the ON clause of the join, in this example using 1.x style queries:

      q = session.query(User).outerjoin(User.addresses).options(
          with_loader_criteria(Address, Address.email_address != 'foo'))
      )

  The primary purpose of `with_loader_criteria()` is to use it in the `SessionEvents.do_orm_execute()` event handler to ensure that all occurrences of a particular entity are filtered in a certain way, such as filtering for access control roles. It also can be used to apply criteria to relationship loads. In the example below, we can apply a certain set of rules to all queries emitted by a particular `Session`:

      session = Session(bind=engine)

      @event.listens_for("do_orm_execute", session)
      def _add_filtering_criteria(execute_state):

          if (
              execute_state.is_select
              and not execute_state.is_column_load
              and not execute_state.is_relationship_load
          ):
              execute_state.statement = execute_state.statement.options(
                  with_loader_criteria(
                      SecurityRole,
                      lambda cls: cls.role.in_(['some_role']),
                      include_aliases=True
                  )
              )

  In the above example, the `SessionEvents.do_orm_execute()` event will intercept all queries emitted using the `Session`. For those queries which are SELECT statements and are not attribute or relationship loads a custom `with_loader_criteria()` option is added to the query. The `with_loader_criteria()` option will be used in the given statement and will also be automatically propagated to all relationship loads that descend from this query.

  The criteria argument given is a `lambda` that accepts a `cls` argument. The given class will expand to include all mapped subclass and need not itself be a mapped class.

  Tip

  When using `with_loader_criteria()` option in conjunction with the `contains_eager()` loader option, it’s important to note that `with_loader_criteria()` only affects the part of the query that determines what SQL is rendered in terms of the WHERE and FROM clauses. The `contains_eager()` option does not affect the rendering of the SELECT statement outside of the columns clause, so does not have any interaction with the `with_loader_criteria()` option. However, the way things “work” is that `contains_eager()` is meant to be used with a query that is already selecting from the additional entities in some way, where `with_loader_criteria()` can apply it’s additional criteria.

  In the example below, assuming a mapping relationship as `A -> A.bs -> B`, the given `with_loader_criteria()` option will affect the way in which the JOIN is rendered:

      stmt = select(A).join(A.bs).options(
          contains_eager(A.bs),
          with_loader_criteria(B, B.flag == 1)
      )

  Above, the given `with_loader_criteria()` option will affect the ON clause of the JOIN that is specified by `.join(A.bs)`, so is applied as expected. The `contains_eager()` option has the effect that columns from `B` are added to the columns clause:

      SELECT
          b.id, b.a_id, b.data, b.flag,
          a.id AS id_1,
          a.data AS data_1
      FROM a JOIN b ON a.id = b.a_id AND b.flag = :flag_1

  The use of the `contains_eager()` option within the above statement has no effect on the behavior of the `with_loader_criteria()` option. If the `contains_eager()` option were omitted, the SQL would be the same as regards the FROM and WHERE clauses, where `with_loader_criteria()` continues to add its criteria to the ON clause of the JOIN. The addition of `contains_eager()` only affects the columns clause, in that additional columns against `b` are added which are then consumed by the ORM to produce `B` instances.

  Warning

  The use of a lambda inside of the call to `with_loader_criteria()` is only invoked once per unique class. Custom functions should not be invoked within this lambda. See Using Lambdas to add significant speed gains to statement production for an overview of the “lambda SQL” feature, which is for advanced use only.

  Parameters

    - entity_or_base – a mapped class, or a class that is a super class of a particular set of mapped classes, to which the rule will apply.

    - where_criteria –

      a Core SQL expression that applies limiting criteria. This may also be a “lambda:” or Python function that accepts a target class as an argument, when the given class is a base with many different mapped subclasses.

      Note

      To support pickling, use a module-level Python function to produce the SQL expression instead of a lambda or a fixed SQL expression, which tend to not be picklable.

    - include_aliases – if True, apply the rule to `aliased()` constructs as well.

    - propagate_to_loaders – defaults to True, apply to relationship loaders such as lazy loaders. This indicates that the option object itself including SQL expression is carried along with each loaded instance. Set to `False` to prevent the object from being assigned to individual instances.

  See also

  ORM Query Events - includes examples of using `with_loader_criteria()`.

  Adding global WHERE / ON criteria - basic example on how to combine `with_loader_criteria()` with the `SessionEvents.do_orm_execute()` event.

  Parameters

    track_closure_variables –

    when False, closure variables inside of a lambda expression will not be used as part of any cache key. This allows more complex expressions to be used inside of a lambda expression but requires that the lambda ensures it returns the identical SQL every time given a particular class.

    New in version 1.4.0b2.

function sqlalchemy.orm.join(left, right, onclause=None, isouter=False, full=False, join_to_left=None)

  Produce an inner join between left and right clauses.

  `join()` is an extension to the core join interface provided by `join()`, where the left and right selectables may be not only core selectable objects such as `Table`, but also mapped classes or `AliasedClass` instances. The “on” clause can be a SQL expression or an ORM mapped attribute referencing a configured `relationship()`.

  Deprecated since version 1.4: using a string relationship name for the “onclause” is deprecated and will be removed in 2.0; the onclause may be only an ORM-mapped relationship attribute or a SQL expression construct.

  `join()` is not commonly needed in modern usage, as its functionality is encapsulated within that of the `Select.join()` and `Query.join()` methods. which feature a significant amount of automation beyond `join()` by itself. Explicit use of `join()` with ORM-enabled SELECT statements involves use of the `Select.select_from()` method, as in:

      from sqlalchemy.orm import join
      stmt = select(User).\
          select_from(join(User, Address, User.addresses)).\
          filter(Address.email_address=='foo@bar.com')

  In modern SQLAlchemy the above join can be written more succinctly as:

      stmt = select(User).\
              join(User.addresses).\
              filter(Address.email_address=='foo@bar.com')

  See Joins for information on modern usage of ORM level joins.

  Deprecated since version 0.8: the `join_to_left` parameter is deprecated, and will be removed in a future release. The parameter has no effect.

function sqlalchemy.orm.outerjoin(left, right, onclause=None, full=False, join_to_left=None)

  Produce a left outer join between left and right clauses.

  This is the “outer join” version of the `join()` function, featuring the same behavior except that an OUTER JOIN is generated. See that function’s documentation for other usage details.

function sqlalchemy.orm.with_parent(instance, prop, from_entity=None)

  Create filtering criterion that relates this query’s primary entity to the given related instance, using established `relationship()` configuration.

  E.g.:

      stmt = select(Address).where(with_parent(some_user, User.addresses))

  The SQL rendered is the same as that rendered when a lazy loader would fire off from the given parent on that attribute, meaning that the appropriate state is taken from the parent object in Python without the need to render joins to the parent table in the rendered statement.

  The given property may also make use of `PropComparator.of_type()` to indicate the left side of the criteria:

      a1 = aliased(Address)
      a2 = aliased(Address)
      stmt = select(a1, a2).where(
          with_parent(u1, User.addresses.of_type(a2))
      )

  The above use is equivalent to using the `from_entity()` argument:

      a1 = aliased(Address)
      a2 = aliased(Address)
      stmt = select(a1, a2).where(
          with_parent(u1, User.addresses, from_entity=a2)
      )

  Parameters

    - instance – An instance which has some `relationship()`.

    - property –

      String property name, or class-bound attribute, which indicates what relationship from the instance should be used to reconcile the parent/child relationship.

      Deprecated since version 1.4: Using strings is deprecated and will be removed in SQLAlchemy 2.0. Please use the class-bound attribute directly.

    - from_entity –

      Entity in which to consider as the left side. This defaults to the “zero” entity of the `Query` itself.

      New in version 1.2.