sqlalchemy.sql.schema.ForeignKeyConstraint

class documentation

class ForeignKeyConstraint(ColumnCollectionConstraint):

A table-level FOREIGN KEY constraint.

Defines a single column or composite FOREIGN KEY ... REFERENCES constraint. For a no-frills, single column foreign key, adding a _schema.ForeignKey to the definition of a _schema.Column is a shorthand equivalent for an unnamed, single column _schema.ForeignKeyConstraint.

Examples of foreign key configuration are in :ref:`metadata_foreignkeys`.

Method	`__init__`	Construct a composite-capable FOREIGN KEY.
Method	`_append_element`	Undocumented
Method	`_copy`	Undocumented
Method	`_set_parent`	Associate with this SchemaEvent's parent object.
Method	`_validate_dest_table`	Undocumented
Method	`copy`	Undocumented
Class Variable	`__visit_name__`	Undocumented
Class Variable	`columns`	A `_expression.ColumnCollection` representing the set of columns for this constraint.
Instance Variable	`elements`	A sequence of `_schema.ForeignKey` objects.
Instance Variable	`link_to_name`	Undocumented
Instance Variable	`match`	Undocumented
Instance Variable	`ondelete`	Undocumented
Instance Variable	`onupdate`	Undocumented
Instance Variable	`use_alter`	Undocumented
Property	`_col_description`	Undocumented
Property	`_elements`	Undocumented
Property	`_referred_schema`	Undocumented
Property	`column_keys`	Return a list of string keys representing the local columns in this `_schema.ForeignKeyConstraint`.
Property	`referred_table`	The `_schema.Table` object to which this `_schema.ForeignKeyConstraint` references.

Inherited from ColumnCollectionConstraint:

Method	`__contains__`	Undocumented
Method	`__iter__`	Undocumented
Method	`__len__`	Undocumented
Method	`contains_column`	Return True if this constraint contains the given column.

Inherited from ColumnCollectionMixin (via ColumnCollectionConstraint):

Method	`_check_attach`	Undocumented
Method	`_col_expressions`	Undocumented
Class Variable	`_allow_multiple_tables`	Undocumented
Instance Variable	`_cols_wo_table`	Undocumented
Instance Variable	`_column_flag`	Undocumented
Instance Variable	`_pending_colargs`	Undocumented

Inherited from Constraint (via ColumnCollectionConstraint):

Instance Variable	`_create_rule`	Undocumented
Instance Variable	`_type_bound`	Undocumented
Instance Variable	`deferrable`	Undocumented
Instance Variable	`info`	Info dictionary associated with the object, allowing user-defined data to be associated with this `.SchemaItem`.
Instance Variable	`initially`	Undocumented
Instance Variable	`name`	Undocumented
Instance Variable	`parent`	Undocumented
Property	`table`	Undocumented

Inherited from DialectKWArgs (via ColumnCollectionConstraint, Constraint):

Class Method	`argument_for`	Add a new kind of dialect-specific keyword argument for this class.
Method	`_kw_reg_for_dialect_cls`	Undocumented
Method	`_validate_dialect_kwargs`	Undocumented
Class Variable	`_dialect_kwargs_traverse_internals`	Undocumented
Class Variable	`_kw_registry`	Undocumented
Property	`dialect_kwargs`	A collection of keyword arguments specified as dialect-specific options to this construct.
Property	`dialect_options`	A collection of keyword arguments specified as dialect-specific options to this construct.
Property	`kwargs`	A synonym for `.DialectKWArgs.dialect_kwargs`.

Inherited from SchemaItem (via ColumnCollectionConstraint, Constraint):

Method	`__repr__`	Undocumented
Method	`_init_items`	Initialize the list of child items for this SchemaItem.
Method	`_schema_item_copy`	Undocumented
Class Variable	`_use_schema_map`	Undocumented
Class Variable	`create_drop_stringify_dialect`	Undocumented

Inherited from SchemaEventTarget (via ColumnCollectionConstraint, Constraint, SchemaItem):

Method _set_parent_with_dispatch Undocumented

Inherited from Traversible (via ColumnCollectionConstraint, Constraint, SchemaItem):

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

def __init__(self, columns, refcolumns, name=None, onupdate=None, ondelete=None, deferrable=None, initially=None, use_alter=False, link_to_name=False, match=None, table=None, info=None, **dialect_kw):

overrides sqlalchemy.sql.schema.ColumnCollectionConstraint.__init__

Construct a composite-capable FOREIGN KEY.

Parameters
columns	A sequence of local column names. The named columns must be defined and present in the parent Table. The names should match the `key` given to each column (defaults to the name) unless `link_to_name` is True.
refcolumns	A sequence of foreign column names or Column objects. The columns must all be located within the same Table.
name	Optional, the in-database name of the key.
onupdate	Optional string. If set, emit ON UPDATE <value> when issuing DDL for this constraint. Typical values include CASCADE, DELETE and RESTRICT.
ondelete	Optional string. If set, emit ON DELETE <value> when issuing DDL for this constraint. Typical values include CASCADE, DELETE and RESTRICT.
deferrable	Optional bool. If set, emit DEFERRABLE or NOT DEFERRABLE when issuing DDL for this constraint.
initially	Optional string. If set, emit INITIALLY <value> when issuing DDL for this constraint.
use_alter	If True, do not emit the DDL for this constraint as part of the CREATE TABLE definition. Instead, generate it via an ALTER TABLE statement issued after the full collection of tables have been created, and drop it via an ALTER TABLE statement before the full collection of tables are dropped. The use of :paramref:`_schema.ForeignKeyConstraint.use_alter` is particularly geared towards the case where two or more tables are established within a mutually-dependent foreign key constraint relationship; however, the `_schema.MetaData.create_all` and `_schema.MetaData.drop_all` methods will perform this resolution automatically, so the flag is normally not needed. Changed in version 1.0.0: Automatic resolution of foreign key cycles has been added, removing the need to use the :paramref:`_schema.ForeignKeyConstraint.use_alter` in typical use cases. See Also :ref:`use_alter`
link_to_name	if True, the string name given in `column` is the rendered name of the referenced column, not its locally assigned `key`.
match	Optional string. If set, emit MATCH <value> when issuing DDL for this constraint. Typical values include SIMPLE, PARTIAL and FULL.
table	Undocumented
info	Optional data dictionary which will be populated into the `.SchemaItem.info` attribute of this object. New in version 1.0.0.
**dialect_kw	Additional keyword arguments are dialect specific, and passed in the form `<dialectname>_<argname>`. See the documentation regarding an individual dialect at :ref:`dialect_toplevel` for detail on documented arguments. New in version 0.9.2.

def _append_element(self, column, fk):

Undocumented

def _copy(self, schema=None, target_table=None, **kw):

overrides sqlalchemy.sql.schema.ColumnCollectionConstraint._copy

Undocumented

def _set_parent(self, table, **kw):

overrides sqlalchemy.sql.schema.ColumnCollectionConstraint._set_parent

Associate with this SchemaEvent's parent object.

def _validate_dest_table(self, table):

Undocumented

@util.deprecated('1.4', 'The :meth:`_schema.ForeignKeyConstraint.copy` method is deprecated and will be removed in a future release.')
def copy(self, schema=None, target_table=None, **kw):

overrides sqlalchemy.sql.schema.ColumnCollectionConstraint.copy

Undocumented

__visit_name__: str =

overrides sqlalchemy.sql.schema.Constraint.__visit_name__

Undocumented

columns =

overrides sqlalchemy.sql.schema.ColumnCollectionConstraint.columns

A _expression.ColumnCollection representing the set of columns for this constraint.

elements =

A sequence of _schema.ForeignKey objects.

Each _schema.ForeignKey represents a single referring column/referred column pair.

This collection is intended to be read-only.

link_to_name =

Undocumented

match =

Undocumented

ondelete =

Undocumented

onupdate =

Undocumented

use_alter =

Undocumented

@property
_col_description =

Undocumented

@property
_elements =

Undocumented

@property
_referred_schema =

Undocumented

@property
column_keys =

Return a list of string keys representing the local columns in this _schema.ForeignKeyConstraint.

This list is either the original string arguments sent to the constructor of the _schema.ForeignKeyConstraint, or if the constraint has been initialized with _schema.Column objects, is the string .key of each element.

New in version 1.0.0.

@property
referred_table =

The _schema.Table object to which this _schema.ForeignKeyConstraint references.

This is a dynamically calculated attribute which may not be available if the constraint and/or parent table is not yet associated with a metadata collection that contains the referred table.

New in version 1.0.0.