Classe « ForeignKeyConstraint »

Constructeur sqlalchemy.ForeignKeyConstraint.__init__

Signature de la constructeur __init__

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) 

Description

__init__.__doc__

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 \**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