sqlalchemy.sql.expression.FromClause

class documentation

class FromClause(roles.AnonymizedFromClauseRole, Selectable):

Known subclasses: sqlalchemy.sql.expression.AliasedReturnsRows, sqlalchemy.sql.expression.Join, sqlalchemy.sql.expression.TableClause, sqlalchemy.sql.expression.Values, sqlalchemy.sql.functions.FunctionElement, sqlalchemy.sql.selectable.FromGrouping

View In Hierarchy

Represent an element that can be used within the FROM clause of a SELECT statement.

The most common forms of _expression.FromClause are the _schema.Table and the _expression.select constructs. Key features common to all _expression.FromClause objects include:

a .c collection, which provides per-name access to a collection of _expression.ColumnElement objects.
a .primary_key attribute, which is a collection of all those _expression.ColumnElement objects that indicate the primary_key flag.
Methods to generate various derivations of a "from" clause, including _expression.FromClause.alias, _expression.FromClause.join, _expression.FromClause.select.

Method	`alias`	Return an alias of this `_expression.FromClause`.
Method	`is_derived_from`	Return `True` if this `_expression.FromClause` is 'derived' from the given `FromClause`.
Method	`join`	Return a `_expression.Join` from this `_expression.FromClause` to another `FromClause`.
Method	`outerjoin`	No summary
Method	`select`	Return a SELECT of this `_expression.FromClause`.
Method	`table_valued`	Return a `_sql.TableValuedColumn` object for this `_expression.FromClause`.
Method	`tablesample`	Return a TABLESAMPLE alias of this `_expression.FromClause`.
Class Variable	`c`	Undocumented
Class Variable	`schema`	Define the 'schema' attribute for this `_expression.FromClause`.
Instance Variable	`foreign_keys`	Return the collection of `_schema.ForeignKey` marker objects which this FromClause references.
Instance Variable	`primary_key`	Return the iterable collection of `_schema.Column` objects which comprise the primary key of this `_selectable.FromClause`.
Method	`_anonymous_fromclause`	Undocumented
Method	`_generate_fromclause_column_proxies`	Undocumented
Method	`_init_collections`	Undocumented
Method	`_is_lexical_equivalent`	Return `True` if this `_expression.FromClause` and the other represent the same lexical identity.
Method	`_populate_column_collection`	Called on subclasses to establish the .c collection.
Method	`_refresh_for_new_column`	Given a column added to the .c collection of an underlying selectable, produce the local version of that column, assuming this selectable ultimately should proxy this column.
Method	`_reset_column_collection`	Reset the attributes linked to the `FromClause.c` attribute.
Class Variable	`__visit_name__`	Undocumented
Class Variable	`_hide_froms`	Undocumented
Class Variable	`_is_from_clause`	Undocumented
Class Variable	`_is_join`	Undocumented
Class Variable	`_select_iterable`	Undocumented
Class Variable	`_use_schema_map`	Undocumented
Class Variable	`is_selectable`	Undocumented
Class Variable	`named_with_column`	Undocumented
Instance Variable	`_columns`	Undocumented
Property	`_cols_populated`	Undocumented
Property	`columns`	A named-based collection of `_expression.ColumnElement` objects maintained by this `_expression.FromClause`.
Property	`description`	A brief description of this `_expression.FromClause`.
Property	`entity_namespace`	Return a namespace used for name-based access in SQL expressions.
Property	`exported_columns`	A `_expression.ColumnCollection` that represents the "exported" columns of this `_expression.Selectable`.

Inherited from FromClauseRole (via AnonymizedFromClauseRole, StrictFromClauseRole):

Class Variable	`_is_subquery`	Undocumented
Class Variable	`_role_name`	Undocumented

Inherited from AllowsLambdaRole (via AnonymizedFromClauseRole, StrictFromClauseRole, FromClauseRole, ColumnsClauseRole):

Class Variable allows_lambda Undocumented

Inherited from UsesInspection (via AnonymizedFromClauseRole, StrictFromClauseRole, FromClauseRole, ColumnsClauseRole):

Class Variable	`_post_inspect`	Undocumented
Class Variable	`uses_inspection`	Undocumented

Inherited from SQLRole (via AnonymizedFromClauseRole, StrictFromClauseRole, FromClauseRole, ColumnsClauseRole, ColumnListRole):

Class Variable	`allows_lambda`	Undocumented
Class Variable	`uses_inspection`	Undocumented

Inherited from AllowsLambdaRole (via AnonymizedFromClauseRole, StrictFromClauseRole, FromClauseRole, JoinTargetRole):

Class Variable allows_lambda Undocumented

Inherited from UsesInspection (via AnonymizedFromClauseRole, StrictFromClauseRole, FromClauseRole, JoinTargetRole):

Class Variable	`_post_inspect`	Undocumented
Class Variable	`uses_inspection`	Undocumented

Inherited from SQLRole (via AnonymizedFromClauseRole, StrictFromClauseRole, FromClauseRole, JoinTargetRole, StructuralRole):

Class Variable	`allows_lambda`	Undocumented
Class Variable	`uses_inspection`	Undocumented

Inherited from Selectable:

Method	`corresponding_column`	No summary
Method	`lateral`	Return a LATERAL alias of this `_expression.Selectable`.
Method	`replace_selectable`	Replace all occurrences of `_expression.FromClause` 'old' with the given `_expression.Alias` object, returning a copy of this `_expression.FromClause`.

Inherited from ReturnsRows (via Selectable):

Class Variable	`_is_lateral`	Undocumented
Class Variable	`_is_returns_rows`	Undocumented
Class Variable	`_is_select_statement`	Undocumented
Property	`_all_selected_columns`	A sequence of column expression objects that represents the "selected" columns of this `_expression.ReturnsRows`.
Property	`selectable`	Undocumented

Inherited from ReturnsRowsRole (via Selectable, ReturnsRows):

Class Variable _role_name Undocumented

Inherited from SQLRole (via Selectable, ReturnsRows, ReturnsRowsRole):

Class Variable	`allows_lambda`	Undocumented
Class Variable	`uses_inspection`	Undocumented

Inherited from ClauseElement (via Selectable, ReturnsRows):

Method	`compare`	Compare this `_expression.ClauseElement` to the given `_expression.ClauseElement`.
Method	`compile`	Compile this SQL expression.
Method	`params`	Return a copy with `_expression.bindparam` elements replaced.
Method	`self_group`	Apply a 'grouping' to this `_expression.ClauseElement`.
Method	`unique_params`	Return a copy with `_expression.bindparam` elements replaced.
Method	`__bool__`	Undocumented
Method	`__getstate__`	Undocumented
Method	`__invert__`	Undocumented
Method	`__repr__`	Undocumented
Method	`__str__`	Undocumented
Method	`_clone`	Create a shallow copy of this ClauseElement.
Method	`_cloned_set`	Return the set consisting all cloned ancestors of this ClauseElement.
Method	`_compile_w_cache`	Undocumented
Method	`_compiler`	Return a compiler appropriate for this ClauseElement, given a Dialect.
Method	`_execute_on_connection`	Undocumented
Method	`_negate`	Undocumented
Method	`_negate_in_binary`	a hook to allow the right side of a binary expression to respond to a negation of the binary expression.
Method	`_replace_params`	Undocumented
Method	`_set_propagate_attrs`	Undocumented
Method	`_ungroup`	Return this `_expression.ClauseElement` without any groupings.
Method	`_with_binary_element_type`	in the context of binary expression, convert the type of this object to the one given.
Class Variable	`_cache_key_traversal`	Undocumented
Class Variable	`_from_objects`	Undocumented
Class Variable	`_is_bind_parameter`	Undocumented
Class Variable	`_is_clause_list`	Undocumented
Class Variable	`_is_clone_of`	Undocumented
Class Variable	`_is_from_container`	Undocumented
Class Variable	`_is_immutable`	Undocumented
Class Variable	`_is_lambda_element`	Undocumented
Class Variable	`_is_select_container`	Undocumented
Class Variable	`_is_singleton_constant`	Undocumented
Class Variable	`_is_text_clause`	Undocumented
Class Variable	`_is_textual`	Undocumented
Class Variable	`_order_by_label_element`	Undocumented
Class Variable	`bind`	Undocumented
Class Variable	`is_clause_element`	Undocumented
Class Variable	`stringify_dialect`	Undocumented
Class Variable	`supports_execution`	Undocumented
Instance Variable	`_propagate_attrs`	like annotations, however these propagate outwards liberally as SQL constructs are built, and are set up at construction time.
Property	`_constructor`	return the 'constructor' for this ClauseElement.

Inherited from SQLRole (via Selectable, ReturnsRows, ClauseElement):

Class Variable	`allows_lambda`	Undocumented
Class Variable	`uses_inspection`	Undocumented

Inherited from SupportsWrappingAnnotations (via Selectable, ReturnsRows, ClauseElement):

Method	`_annotate`	return a copy of this ClauseElement with annotations updated by the given dictionary.
Method	`_deannotate`	return a copy of this `_expression.ClauseElement` with annotations removed.
Method	`_with_annotations`	return a copy of this ClauseElement with annotations replaced by the given dictionary.

Inherited from SupportsAnnotations (via Selectable, ReturnsRows, ClauseElement, SupportsWrappingAnnotations):

Property _annotations_cache_key Undocumented

Inherited from MemoizedHasCacheKey (via Selectable, ReturnsRows, ClauseElement):

Method _generate_cache_key return a cache key.

Inherited from HasCacheKey (via Selectable, ReturnsRows, ClauseElement, MemoizedHasCacheKey):

Class Variable	`inherit_cache`	Indicate if this `.HasCacheKey` instance should make use of the cache key generation scheme used by its immediate superclass.
Class Method	`_generate_cache_attrs`	generate cache key dispatcher for a new class.
Class Method	`_generate_cache_key_for_object`	Undocumented
Method	`_gen_cache_key`	return an optional cache key.
Class Variable	`__slots__`	Undocumented
Class Variable	`_hierarchy_supports_caching`	private attribute which may be set to False to prevent the inherit_cache warning from being emitted for a hierarchy of subclasses.
Class Variable	`_is_has_cache_key`	Undocumented

Inherited from HasCopyInternals (via Selectable, ReturnsRows, ClauseElement):

Method _copy_internals Reassign internal elements to be clones of themselves.

Inherited from Traversible (via Selectable, ReturnsRows, ClauseElement):

Method	`get_children`	Return immediate child `.visitors.Traversible` elements of this `.visitors.Traversible`.
Method	`__class_getitem__`	Undocumented

def alias(self, name=None, flat=False):

overridden in sqlalchemy.sql.expression.Join, sqlalchemy.sql.expression.TableValuedAlias, sqlalchemy.sql.expression.Values, sqlalchemy.sql.functions.FunctionElement, sqlalchemy.sql.selectable.CTE, sqlalchemy.sql.selectable.FromGrouping

Return an alias of this _expression.FromClause.

E.g.:

a2 = some_table.alias('a2')

The above code creates an _expression.Alias object which can be used as a FROM clause in any SELECT statement.

See Also

:ref:`core_tutorial_aliases`

_expression.alias

def is_derived_from(self, fromclause):

overridden in sqlalchemy.sql.expression.AliasedReturnsRows, sqlalchemy.sql.expression.Join, sqlalchemy.sql.selectable.FromGrouping

Return True if this _expression.FromClause is 'derived' from the given FromClause.

An example would be an Alias of a Table is derived from that Table.

def join(self, right, onclause=None, isouter=False, full=False):

overridden in sqlalchemy.orm.util._ORMJoin

Return a _expression.Join from this _expression.FromClause to another FromClause.

E.g.:

from sqlalchemy import join

j = user_table.join(address_table,
                user_table.c.id == address_table.c.user_id)
stmt = select(user_table).select_from(j)

would emit SQL along the lines of:

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

See Also

_expression.join - standalone function

_expression.Join - the type of object produced

Parameters
right	the right side of the join; this is any `_expression.FromClause` object such as a `_schema.Table` object, and may also be a selectable-compatible object such as an ORM-mapped class.
onclause	a SQL expression representing the ON clause of the join. If left at `None`, `_expression.FromClause.join` will attempt to join the two tables based on a foreign key relationship.
isouter	if True, render a LEFT OUTER JOIN, instead of JOIN.
full	if True, render a FULL OUTER JOIN, instead of LEFT OUTER JOIN. Implies :paramref:`.FromClause.join.isouter`. New in version 1.1.

def outerjoin(self, right, onclause=None, full=False):

overridden in sqlalchemy.orm.util._ORMJoin

Return a _expression.Join from this _expression.FromClause to another FromClause, with the "isouter" flag set to True.

E.g.:

from sqlalchemy import outerjoin

j = user_table.outerjoin(address_table,
                user_table.c.id == address_table.c.user_id)

The above is equivalent to:

j = user_table.join(
    address_table,
    user_table.c.id == address_table.c.user_id,
    isouter=True)

See Also

_expression.FromClause.join

_expression.Join

Parameters
right	the right side of the join; this is any `_expression.FromClause` object such as a `_schema.Table` object, and may also be a selectable-compatible object such as an ORM-mapped class.
onclause	a SQL expression representing the ON clause of the join. If left at `None`, `_expression.FromClause.join` will attempt to join the two tables based on a foreign key relationship.
full	if True, render a FULL OUTER JOIN, instead of LEFT OUTER JOIN. New in version 1.1.

@util.deprecated_params(whereclause=('2.0', 'The :paramref:`_sql.FromClause.select().whereclause` parameter is deprecated and will be removed in version 2.0. Please make use of the :meth:`.Select.where` method to add WHERE criteria to the SELECT statement.'), kwargs=('2.0', 'The :meth:`_sql.FromClause.select` method will no longer accept keyword arguments in version 2.0. Please use generative methods from the :class:`_sql.Select` construct in order to apply additional modifications.'))
def select(self, whereclause=None, **kwargs):

overridden in sqlalchemy.sql.expression.Join, sqlalchemy.sql.functions.FunctionElement

Return a SELECT of this _expression.FromClause.

e.g.:

stmt = some_table.select().where(some_table.c.id == 5)

See Also

_expression.select - general purpose method which allows for arbitrary column lists.

Parameters
whereclause	a WHERE clause, equivalent to calling the `_sql.Select.where` method.
**kwargs	additional keyword arguments are passed to the legacy constructor for `_sql.Select` described at `_sql.Select.create_legacy_select`.

@util.preload_module('sqlalchemy.sql.sqltypes')
def table_valued(self):

overridden in sqlalchemy.sql.functions.FunctionElement

Return a _sql.TableValuedColumn object for this _expression.FromClause.

A _sql.TableValuedColumn is a _sql.ColumnElement that represents a complete row in a table. Support for this construct is backend dependent, and is supported in various forms by backends such as PostgreSQL, Oracle and SQL Server.

E.g.:

>>> from sqlalchemy import select, column, func, table
>>> a = table("a", column("id"), column("x"), column("y"))
>>> stmt = select(func.row_to_json(a.table_valued()))
>>> print(stmt)
SELECT row_to_json(a) AS row_to_json_1
FROM a

New in version 1.4.0b2.

def tablesample(self, sampling, name=None, seed=None):

Return a TABLESAMPLE alias of this _expression.FromClause.

The return value is the _expression.TableSample construct also provided by the top-level _expression.tablesample function.

New in version 1.1.

See Also

_expression.tablesample - usage guidelines and parameters

c =

Undocumented

schema =

overridden in sqlalchemy.sql.expression.TableClause

Define the 'schema' attribute for this _expression.FromClause.

This is typically None for most objects except that of _schema.Table, where it is taken as the value of the :paramref:`_schema.Table.schema` argument.

@util.memoized_property
foreign_keys: set =

overridden in sqlalchemy.sql.expression.TableClause, sqlalchemy.sql.selectable.FromGrouping

Return the collection of _schema.ForeignKey marker objects which this FromClause references.

Each _schema.ForeignKey is a member of a _schema.Table-wide _schema.ForeignKeyConstraint.

See Also

_schema.Table.foreign_key_constraints

@util.memoized_property
primary_key =

overridden in sqlalchemy.sql.expression.TableClause, sqlalchemy.sql.selectable.FromGrouping

Return the iterable collection of _schema.Column objects which comprise the primary key of this _selectable.FromClause.

For a _schema.Table object, this collection is represented by the _schema.PrimaryKeyConstraint which itself is an iterable collection of _schema.Column objects.

def _anonymous_fromclause(self, name=None, flat=False):

overrides sqlalchemy.sql.roles.AnonymizedFromClauseRole._anonymous_fromclause

overridden in sqlalchemy.sql.expression.Join, sqlalchemy.sql.selectable.FromGrouping

Undocumented

def _generate_fromclause_column_proxies(self, fromclause):

Undocumented

def _init_collections(self):

overridden in sqlalchemy.sql.expression.TableClause, sqlalchemy.sql.selectable.FromGrouping

Undocumented

def _is_lexical_equivalent(self, other):

Return True if this _expression.FromClause and the other represent the same lexical identity.

This tests if either one is a copy of the other, or if they are the same via annotation identity.

def _populate_column_collection(self):

overridden in sqlalchemy.sql.expression.AliasedReturnsRows, sqlalchemy.sql.expression.Join, sqlalchemy.sql.expression.Values

Called on subclasses to establish the .c collection.

Each implementation has a different way of establishing this collection.

def _refresh_for_new_column(self, column):

overrides sqlalchemy.sql.expression.Selectable._refresh_for_new_column

overridden in sqlalchemy.sql.expression.AliasedReturnsRows, sqlalchemy.sql.expression.Join, sqlalchemy.sql.expression.TableClause

Given a column added to the .c collection of an underlying selectable, produce the local version of that column, assuming this selectable ultimately should proxy this column.

this is used to "ping" a derived selectable to add a new column to its .c. collection when a Column has been added to one of the Table objects it ultimately derives from.

If the given selectable hasn't populated its .c. collection yet, it should at least pass on the message to the contained selectables, but it will return None.

This method is currently used by Declarative to allow Table columns to be added to a partially constructed inheritance mapping that may have already produced joins. The method isn't public right now, as the full span of implications and/or caveats aren't yet clear.

It's also possible that this functionality could be invoked by default via an event, which would require that selectables maintain a weak referencing collection of all derivations.

def _reset_column_collection(self):

Reset the attributes linked to the FromClause.c attribute.

This collection is separate from all the other memoized things as it has shown to be sensitive to being cleared out in situations where enclosing code, typically in a replacement traversal scenario, has already established strong relationships with the exported columns.

The collection is cleared for the case where a table is having a column added to it as well as within a Join during copy internals.

__visit_name__: str =

overrides sqlalchemy.sql.expression.Selectable.__visit_name__

overridden in sqlalchemy.sql.expression.Alias, sqlalchemy.sql.expression.Join, sqlalchemy.sql.expression.Lateral, sqlalchemy.sql.expression.Subquery, sqlalchemy.sql.expression.TableClause, sqlalchemy.sql.expression.TableSample, sqlalchemy.sql.expression.Values, sqlalchemy.sql.functions.Function, sqlalchemy.sql.selectable.CTE

Undocumented

_hide_froms: list =

overrides sqlalchemy.sql.roles.FromClauseRole._hide_froms

overridden in sqlalchemy.sql.expression.Join, sqlalchemy.sql.selectable.FromGrouping

Undocumented

_is_from_clause: bool =

overrides sqlalchemy.sql.selectable.ReturnsRows._is_from_clause

Undocumented

_is_join: bool =

overridden in sqlalchemy.sql.expression.Join

Undocumented

_select_iterable =

overrides sqlalchemy.sql.roles.ColumnsClauseRole._select_iterable

Undocumented

_use_schema_map: bool =

Undocumented

is_selectable: bool =

overrides sqlalchemy.sql.expression.Selectable.is_selectable

Undocumented

named_with_column: bool =

overridden in sqlalchemy.sql.expression.AliasedReturnsRows, sqlalchemy.sql.expression.TableClause, sqlalchemy.sql.expression.Values

Undocumented

_columns =

overridden in sqlalchemy.sql.expression.TableClause

Undocumented

@property
_cols_populated =

Undocumented

@util.memoized_property
columns =

overridden in sqlalchemy.sql.functions.FunctionElement, sqlalchemy.sql.selectable.FromGrouping

A named-based collection of _expression.ColumnElement objects maintained by this _expression.FromClause.

The .columns, or .c collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:

select(mytable).where(mytable.c.somecolumn == 5)

@property
description =

overrides sqlalchemy.sql.roles.StrictFromClauseRole.description

overridden in sqlalchemy.sql.expression.AliasedReturnsRows, sqlalchemy.sql.expression.Join, sqlalchemy.sql.expression.TableClause

A brief description of this _expression.FromClause.

Used primarily for error message formatting.

@property
entity_namespace =

overrides sqlalchemy.sql.expression.ClauseElement.entity_namespace

overridden in sqlalchemy.sql.functions.FunctionElement

Return a namespace used for name-based access in SQL expressions.

This is the namespace that is used to resolve "filter_by()" type expressions, such as:

stmt.filter_by(address='some address')

It defaults to the .c collection, however internally it can be overridden using the "entity_namespace" annotation to deliver alternative results.

@property
exported_columns =

overrides sqlalchemy.sql.selectable.ReturnsRows.exported_columns

overridden in sqlalchemy.sql.functions.FunctionElement

A _expression.ColumnCollection that represents the "exported" columns of this _expression.Selectable.

The "exported" columns for a _expression.FromClause object are synonymous with the _expression.FromClause.columns collection.

New in version 1.4.

See Also

_expression.Selectable.exported_columns

_expression.SelectBase.exported_columns