我们从Python开源项目中，提取了以下14个代码示例，用于说明如何使用sqlalchemy.schema.Constraint()。
def generic_constraint(self, name, table_name, type_, schema=None, **kw): t = self.table(table_name, schema=schema) types = { 'foreignkey': lambda name: sa_schema.ForeignKeyConstraint( [], [], name=name), 'primary': sa_schema.PrimaryKeyConstraint, 'unique': sa_schema.UniqueConstraint, 'check': lambda name: sa_schema.CheckConstraint("", name=name), None: sa_schema.Constraint } try: const = types[type_] except KeyError: raise TypeError("'type' can be one of %s" % ", ".join(sorted(repr(x) for x in types))) else: const = const(name=name) t.append_constraint(const) return const
def drop_constraint(self, name, table_name, type_=None, schema=None): """Drop a constraint of the given name, typically via DROP CONSTRAINT. :param name: name of the constraint. :param table_name: table name. :param ``type_``: optional, required on MySQL. can be 'foreignkey', 'primary', 'unique', or 'check'. :param schema: Optional schema name to operate within. To control quoting of the schema outside of the default behavior, use the SQLAlchemy construct :class:`~sqlalchemy.sql.elements.quoted_name`. .. versionadded:: 0.7.0 'schema' can now accept a :class:`~sqlalchemy.sql.elements.quoted_name` construct. """ t = self._table(table_name, schema=schema) types = { 'foreignkey': lambda name: sa_schema.ForeignKeyConstraint( [], [], name=name), 'primary': sa_schema.PrimaryKeyConstraint, 'unique': sa_schema.UniqueConstraint, 'check': lambda name: sa_schema.CheckConstraint("", name=name), None: sa_schema.Constraint } try: const = types[type_] except KeyError: raise TypeError("'type' can be one of %s" % ", ".join(sorted(repr(x) for x in types))) const = const(name=name) t.append_constraint(const) self.impl.drop_constraint(const)
def create_table(self, name, *columns, **kw): """Issue a "create table" instruction using the current migration context. This directive receives an argument list similar to that of the traditional :class:`sqlalchemy.schema.Table` construct, but without the metadata:: from sqlalchemy import INTEGER, VARCHAR, NVARCHAR, Column from alembic import op op.create_table( 'account', Column('id', INTEGER, primary_key=True), Column('name', VARCHAR(50), nullable=False), Column('description', NVARCHAR(200)) Column('timestamp', TIMESTAMP, server_default=func.now()) ) Note that :meth:`.create_table` accepts :class:`~sqlalchemy.schema.Column` constructs directly from the SQLAlchemy library. In particular, default values to be created on the database side are specified using the ``server_default`` parameter, and not ``default`` which only specifies Python-side defaults:: from alembic import op from sqlalchemy import Column, TIMESTAMP, func # specify "DEFAULT NOW" along with the "timestamp" column op.create_table('account', Column('id', INTEGER, primary_key=True), Column('timestamp', TIMESTAMP, server_default=func.now()) ) :param name: Name of the table :param \*columns: collection of :class:`~sqlalchemy.schema.Column` objects within the table, as well as optional :class:`~sqlalchemy.schema.Constraint` objects and :class:`~.sqlalchemy.schema.Index` objects. :param schema: Optional schema name to operate within. :param \**kw: Other keyword arguments are passed to the underlying :class:`sqlalchemy.schema.Table` object created for the command. """ self.impl.create_table( self._table(name, *columns, **kw) )
def drop_constraint(self, name, table_name, type_=None, schema=None): """Drop a constraint of the given name, typically via DROP CONSTRAINT. :param name: name of the constraint. :param table_name: table name. .. versionchanged:: 0.5.0 The ``tablename`` parameter is now named ``table_name``. As this is a positional argument, the old name is no longer present. :param ``type_``: optional, required on MySQL. can be 'foreignkey', 'primary', 'unique', or 'check'. .. versionchanged:: 0.5.0 The ``type`` parameter is now named ``type_``. The old name ``type`` will remain for backwards compatibility. .. versionadded:: 0.3.6 'primary' qualfier to enable dropping of MySQL primary key constraints. :param schema: Optional schema name to operate within. .. versionadded:: 0.4.0 """ t = self._table(table_name, schema=schema) types = { 'foreignkey': lambda name: sa_schema.ForeignKeyConstraint( [], [], name=name), 'primary': sa_schema.PrimaryKeyConstraint, 'unique': sa_schema.UniqueConstraint, 'check': lambda name: sa_schema.CheckConstraint("", name=name), None: sa_schema.Constraint } try: const = types[type_] except KeyError: raise TypeError("'type' can be one of %s" % ", ".join(sorted(repr(x) for x in types))) const = const(name=name) t.append_constraint(const) self.impl.drop_constraint(const)
