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_selectable_constructors.py
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# sql/_selectable_constructors.py # Copyright (C) 2005-2024 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: https://www.opensource.org/licenses/mit-license.php from __future__ import annotations from typing import Any from typing import Optional from typing import overload from typing import Tuple from typing import TYPE_CHECKING from typing import TypeVar from typing import Union from . import coercions from . import roles from ._typing import _ColumnsClauseArgument from ._typing import _no_kw from .elements import ColumnClause from .selectable import Alias from .selectable import CompoundSelect from .selectable import Exists from .selectable import FromClause from .selectable import Join from .selectable import Lateral from .selectable import LateralFromClause from .selectable import NamedFromClause from .selectable import Select from .selectable import TableClause from .selectable import TableSample from .selectable import Values if TYPE_CHECKING: from ._typing import _FromClauseArgument from ._typing import _OnClauseArgument from ._typing import _SelectStatementForCompoundArgument from ._typing import _T0 from ._typing import _T1 from ._typing import _T2 from ._typing import _T3 from ._typing import _T4 from ._typing import _T5 from ._typing import _T6 from ._typing import _T7 from ._typing import _T8 from ._typing import _T9 from ._typing import _TypedColumnClauseArgument as _TCCA from .functions import Function from .selectable import CTE from .selectable import HasCTE from .selectable import ScalarSelect from .selectable import SelectBase _T = TypeVar("_T", bound=Any) def alias( selectable: FromClause, name: Optional[str] = None, flat: bool = False ) -> NamedFromClause: """Return a named alias of the given :class:`.FromClause`. For :class:`.Table` and :class:`.Join` objects, the return type is the :class:`_expression.Alias` object. Other kinds of :class:`.NamedFromClause` objects may be returned for other kinds of :class:`.FromClause` objects. The named alias represents any :class:`_expression.FromClause` with an alternate name assigned within SQL, typically using the ``AS`` clause when generated, e.g. ``SELECT * FROM table AS aliasname``. Equivalent functionality is available via the :meth:`_expression.FromClause.alias` method available on all :class:`_expression.FromClause` objects. :param selectable: any :class:`_expression.FromClause` subclass, such as a table, select statement, etc. :param name: string name to be assigned as the alias. If ``None``, a name will be deterministically generated at compile time. Deterministic means the name is guaranteed to be unique against other constructs used in the same statement, and will also be the same name for each successive compilation of the same statement object. :param flat: Will be passed through to if the given selectable is an instance of :class:`_expression.Join` - see :meth:`_expression.Join.alias` for details. """ return Alias._factory(selectable, name=name, flat=flat) def cte( selectable: HasCTE, name: Optional[str] = None, recursive: bool = False ) -> CTE: r"""Return a new :class:`_expression.CTE`, or Common Table Expression instance. Please see :meth:`_expression.HasCTE.cte` for detail on CTE usage. """ return coercions.expect(roles.HasCTERole, selectable).cte( name=name, recursive=recursive ) def except_( *selects: _SelectStatementForCompoundArgument, ) -> CompoundSelect: r"""Return an ``EXCEPT`` of multiple selectables. The returned object is an instance of :class:`_expression.CompoundSelect`. :param \*selects: a list of :class:`_expression.Select` instances. """ return CompoundSelect._create_except(*selects) def except_all( *selects: _SelectStatementForCompoundArgument, ) -> CompoundSelect: r"""Return an ``EXCEPT ALL`` of multiple selectables. The returned object is an instance of :class:`_expression.CompoundSelect`. :param \*selects: a list of :class:`_expression.Select` instances. """ return CompoundSelect._create_except_all(*selects) def exists( __argument: Optional[ Union[_ColumnsClauseArgument[Any], SelectBase, ScalarSelect[Any]] ] = None, ) -> Exists: """Construct a new :class:`_expression.Exists` construct. The :func:`_sql.exists` can be invoked by itself to produce an :class:`_sql.Exists` construct, which will accept simple WHERE criteria:: exists_criteria = exists().where(table1.c.col1 == table2.c.col2) However, for greater flexibility in constructing the SELECT, an existing :class:`_sql.Select` construct may be converted to an :class:`_sql.Exists`, most conveniently by making use of the :meth:`_sql.SelectBase.exists` method:: exists_criteria = ( select(table2.c.col2). where(table1.c.col1 == table2.c.col2). exists() ) The EXISTS criteria is then used inside of an enclosing SELECT:: stmt = select(table1.c.col1).where(exists_criteria) The above statement will then be of the form:: SELECT col1 FROM table1 WHERE EXISTS (SELECT table2.col2 FROM table2 WHERE table2.col2 = table1.col1) .. seealso:: :ref:`tutorial_exists` - in the :term:`2.0 style` tutorial. :meth:`_sql.SelectBase.exists` - method to transform a ``SELECT`` to an ``EXISTS`` clause. """ # noqa: E501 return Exists(__argument) def intersect( *selects: _SelectStatementForCompoundArgument, ) -> CompoundSelect: r"""Return an ``INTERSECT`` of multiple selectables. The returned object is an instance of :class:`_expression.CompoundSelect`. :param \*selects: a list of :class:`_expression.Select` instances. """ return CompoundSelect._create_intersect(*selects) def intersect_all( *selects: _SelectStatementForCompoundArgument, ) -> CompoundSelect: r"""Return an ``INTERSECT ALL`` of multiple selectables. The returned object is an instance of :class:`_expression.CompoundSelect`. :param \*selects: a list of :class:`_expression.Select` instances. """ return CompoundSelect._create_intersect_all(*selects) def join( left: _FromClauseArgument, right: _FromClauseArgument, onclause: Optional[_OnClauseArgument] = None, isouter: bool = False, full: bool = False, ) -> Join: """Produce a :class:`_expression.Join` object, given two :class:`_expression.FromClause` expressions. E.g.:: j = join(user_table, address_table, user_table.c.id == address_table.c.user_id) stmt = select(user_table).select_from(j) would emit SQL along the lines of:: SELECT user.id, user.name FROM user JOIN address ON user.id = address.user_id Similar functionality is available given any :class:`_expression.FromClause` object (e.g. such as a :class:`_schema.Table`) using the :meth:`_expression.FromClause.join` method. :param left: The left side of the join. :param right: the right side of the join; this is any :class:`_expression.FromClause` object such as a :class:`_schema.Table` object, and may also be a selectable-compatible object such as an ORM-mapped class. :param onclause: a SQL expression representing the ON clause of the join. If left at ``None``, :meth:`_expression.FromClause.join` will attempt to join the two tables based on a foreign key relationship. :param isouter: if True, render a LEFT OUTER JOIN, instead of JOIN. :param full: if True, render a FULL OUTER JOIN, instead of JOIN. .. seealso:: :meth:`_expression.FromClause.join` - method form, based on a given left side. :class:`_expression.Join` - the type of object produced. """ return Join(left, right, onclause, isouter, full) def lateral( selectable: Union[SelectBase, _FromClauseArgument], name: Optional[str] = None, ) -> LateralFromClause: """Return a :class:`_expression.Lateral` object. :class:`_expression.Lateral` is an :class:`_expression.Alias` subclass that represents a subquery with the LATERAL keyword applied to it. The special behavior of a LATERAL subquery is that it appears in the FROM clause of an enclosing SELECT, but may correlate to other FROM clauses of that SELECT. It is a special case of subquery only supported by a small number of backends, currently more recent PostgreSQL versions. .. seealso:: :ref:`tutorial_lateral_correlation` - overview of usage. """ return Lateral._factory(selectable, name=name) def outerjoin( left: _FromClauseArgument, right: _FromClauseArgument, onclause: Optional[_OnClauseArgument] = None, full: bool = False, ) -> Join: """Return an ``OUTER JOIN`` clause element. The returned object is an instance of :class:`_expression.Join`. Similar functionality is also available via the :meth:`_expression.FromClause.outerjoin` method on any :class:`_expression.FromClause`. :param left: The left side of the join. :param right: The right side of the join. :param onclause: Optional criterion for the ``ON`` clause, is derived from foreign key relationships established between left and right otherwise. To chain joins together, use the :meth:`_expression.FromClause.join` or :meth:`_expression.FromClause.outerjoin` methods on the resulting :class:`_expression.Join` object. """ return Join(left, right, onclause, isouter=True, full=full) # START OVERLOADED FUNCTIONS select Select 1-10 # code within this block is **programmatically, # statically generated** by tools/generate_tuple_map_overloads.py @overload def select(__ent0: _TCCA[_T0]) -> Select[Tuple[_T0]]: ... @overload def select( __ent0: _TCCA[_T0], __ent1: _TCCA[_T1] ) -> Select[Tuple[_T0, _T1]]: ... @overload def select( __ent0: _TCCA[_T0], __ent1: _TCCA[_T1], __ent2: _TCCA[_T2] ) -> Select[Tuple[_T0, _T1, _T2]]: ... @overload def select( __ent0: _TCCA[_T0], __ent1: _TCCA[_T1], __ent2: _TCCA[_T2], __ent3: _TCCA[_T3], ) -> Select[Tuple[_T0, _T1, _T2, _T3]]: ... @overload def select( __ent0: _TCCA[_T0], __ent1: _TCCA[_T1], __ent2: _TCCA[_T2], __ent3: _TCCA[_T3], __ent4: _TCCA[_T4], ) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4]]: ... @overload def select( __ent0: _TCCA[_T0], __ent1: _TCCA[_T1], __ent2: _TCCA[_T2], __ent3: _TCCA[_T3], __ent4: _TCCA[_T4], __ent5: _TCCA[_T5], ) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4, _T5]]: ... @overload def select( __ent0: _TCCA[_T0], __ent1: _TCCA[_T1], __ent2: _TCCA[_T2], __ent3: _TCCA[_T3], __ent4: _TCCA[_T4], __ent5: _TCCA[_T5], __ent6: _TCCA[_T6], ) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4, _T5, _T6]]: ... @overload def select( __ent0: _TCCA[_T0], __ent1: _TCCA[_T1], __ent2: _TCCA[_T2], __ent3: _TCCA[_T3], __ent4: _TCCA[_T4], __ent5: _TCCA[_T5], __ent6: _TCCA[_T6], __ent7: _TCCA[_T7], ) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4, _T5, _T6, _T7]]: ... @overload def select( __ent0: _TCCA[_T0], __ent1: _TCCA[_T1], __ent2: _TCCA[_T2], __ent3: _TCCA[_T3], __ent4: _TCCA[_T4], __ent5: _TCCA[_T5], __ent6: _TCCA[_T6], __ent7: _TCCA[_T7], __ent8: _TCCA[_T8], ) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4, _T5, _T6, _T7, _T8]]: ... @overload def select( __ent0: _TCCA[_T0], __ent1: _TCCA[_T1], __ent2: _TCCA[_T2], __ent3: _TCCA[_T3], __ent4: _TCCA[_T4], __ent5: _TCCA[_T5], __ent6: _TCCA[_T6], __ent7: _TCCA[_T7], __ent8: _TCCA[_T8], __ent9: _TCCA[_T9], ) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4, _T5, _T6, _T7, _T8, _T9]]: ... # END OVERLOADED FUNCTIONS select @overload def select( *entities: _ColumnsClauseArgument[Any], **__kw: Any ) -> Select[Any]: ... def select(*entities: _ColumnsClauseArgument[Any], **__kw: Any) -> Select[Any]: r"""Construct a new :class:`_expression.Select`. .. versionadded:: 1.4 - The :func:`_sql.select` function now accepts column arguments positionally. The top-level :func:`_sql.select` function will automatically use the 1.x or 2.x style API based on the incoming arguments; using :func:`_sql.select` from the ``sqlalchemy.future`` module will enforce that only the 2.x style constructor is used. Similar functionality is also available via the :meth:`_expression.FromClause.select` method on any :class:`_expression.FromClause`. .. seealso:: :ref:`tutorial_selecting_data` - in the :ref:`unified_tutorial` :param \*entities: Entities to SELECT from. For Core usage, this is typically a series of :class:`_expression.ColumnElement` and / or :class:`_expression.FromClause` objects which will form the columns clause of the resulting statement. For those objects that are instances of :class:`_expression.FromClause` (typically :class:`_schema.Table` or :class:`_expression.Alias` objects), the :attr:`_expression.FromClause.c` collection is extracted to form a collection of :class:`_expression.ColumnElement` objects. This parameter will also accept :class:`_expression.TextClause` constructs as given, as well as ORM-mapped classes. """ # the keyword args are a necessary element in order for the typing # to work out w/ the varargs vs. having named "keyword" arguments that # aren't always present. if __kw: raise _no_kw() return Select(*entities) def table(name: str, *columns: ColumnClause[Any], **kw: Any) -> TableClause: """Produce a new :class:`_expression.TableClause`. The object returned is an instance of :class:`_expression.TableClause`, which represents the "syntactical" portion of the schema-level :class:`_schema.Table` object. It may be used to construct lightweight table constructs. :param name: Name of the table. :param columns: A collection of :func:`_expression.column` constructs. :param schema: The schema name for this table. .. versionadded:: 1.3.18 :func:`_expression.table` can now accept a ``schema`` argument. """ return TableClause(name, *columns, **kw) def tablesample( selectable: _FromClauseArgument, sampling: Union[float, Function[Any]], name: Optional[str] = None, seed: Optional[roles.ExpressionElementRole[Any]] = None, ) -> TableSample: """Return a :class:`_expression.TableSample` object. :class:`_expression.TableSample` is an :class:`_expression.Alias` subclass that represents a table with the TABLESAMPLE clause applied to it. :func:`_expression.tablesample` is also available from the :class:`_expression.FromClause` class via the :meth:`_expression.FromClause.tablesample` method. The TABLESAMPLE clause allows selecting a randomly selected approximate percentage of rows from a table. It supports multiple sampling methods, most commonly BERNOULLI and SYSTEM. e.g.:: from sqlalchemy import func selectable = people.tablesample( func.bernoulli(1), name='alias', seed=func.random()) stmt = select(selectable.c.people_id) Assuming ``people`` with a column ``people_id``, the above statement would render as:: SELECT alias.people_id FROM people AS alias TABLESAMPLE bernoulli(:bernoulli_1) REPEATABLE (random()) :param sampling: a ``float`` percentage between 0 and 100 or :class:`_functions.Function`. :param name: optional alias name :param seed: any real-valued SQL expression. When specified, the REPEATABLE sub-clause is also rendered. """ return TableSample._factory(selectable, sampling, name=name, seed=seed) def union( *selects: _SelectStatementForCompoundArgument, ) -> CompoundSelect: r"""Return a ``UNION`` of multiple selectables. The returned object is an instance of :class:`_expression.CompoundSelect`. A similar :func:`union()` method is available on all :class:`_expression.FromClause` subclasses. :param \*selects: a list of :class:`_expression.Select` instances. :param \**kwargs: available keyword arguments are the same as those of :func:`select`. """ return CompoundSelect._create_union(*selects) def union_all( *selects: _SelectStatementForCompoundArgument, ) -> CompoundSelect: r"""Return a ``UNION ALL`` of multiple selectables. The returned object is an instance of :class:`_expression.CompoundSelect`. A similar :func:`union_all()` method is available on all :class:`_expression.FromClause` subclasses. :param \*selects: a list of :class:`_expression.Select` instances. """ return CompoundSelect._create_union_all(*selects) def values( *columns: ColumnClause[Any], name: Optional[str] = None, literal_binds: bool = False, ) -> Values: r"""Construct a :class:`_expression.Values` construct. The column expressions and the actual data for :class:`_expression.Values` are given in two separate steps. The constructor receives the column expressions typically as :func:`_expression.column` constructs, and the data is then passed via the :meth:`_expression.Values.data` method as a list, which can be called multiple times to add more data, e.g.:: from sqlalchemy import column from sqlalchemy import values value_expr = values( column('id', Integer), column('name', String), name="my_values" ).data( [(1, 'name1'), (2, 'name2'), (3, 'name3')] ) :param \*columns: column expressions, typically composed using :func:`_expression.column` objects. :param name: the name for this VALUES construct. If omitted, the VALUES construct will be unnamed in a SQL expression. Different backends may have different requirements here. :param literal_binds: Defaults to False. Whether or not to render the data values inline in the SQL output, rather than using bound parameters. """ return Values(*columns, literal_binds=literal_binds, name=name)