sqlalchemy.sql.schema.ForeignKeyConstraint

Construct a composite-capable FOREIGN KEY. :param 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. :param refcolumns: A sequence of foreign column names or Column objects. The columns must all be located within the same Table. :param name: Optional, the in-database name of the key. :param onupdate: Optional string. If set, emit ON UPDATE <value> when issuing DDL for this constraint. Typical values include CASCADE, DELETE and RESTRICT. :param ondelete: Optional string. If set, emit ON DELETE <value> when issuing DDL for this constraint. Typical values include CASCADE, DELETE and RESTRICT. :param deferrable: Optional bool. If set, emit DEFERRABLE or NOT DEFERRABLE when issuing DDL for this constraint. :param initially: Optional string. If set, emit INITIALLY <value> when issuing DDL for this constraint. :param link_to_name: if True, the string name given in ``column`` is the rendered name of the referenced column, not its locally assigned ``key``. :param 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 :meth:`_schema.MetaData.create_all` and :meth:`_schema.MetaData.drop_all` methods will perform this resolution automatically, so the flag is normally not needed. .. versionchanged:: 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. .. seealso:: :ref:`use_alter` :param match: Optional string. If set, emit MATCH <value> when issuing DDL for this constraint. Typical values include SIMPLE, PARTIAL and FULL. :param info: Optional data dictionary which will be populated into the :attr:`.SchemaItem.info` attribute of this object. .. versionadded:: 1.0.0 :param comment: Optional string that will render an SQL comment on foreign key constraint creation. .. versionadded:: 2.0 :param \**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. .. versionadded:: 0.9.2

Undocumented