elements.py 文件源码

def _create_desc(cls, column):
        """Produce a descending ``ORDER BY`` clause element.

        e.g.::

            from sqlalchemy import desc

            stmt = select([users_table]).order_by(desc(users_table.c.name))

        will produce SQL as::

            SELECT id, name FROM user ORDER BY name DESC

        The :func:`.desc` function is a standalone version of the
        :meth:`.ColumnElement.desc` method available on all SQL expressions,
        e.g.::


            stmt = select([users_table]).order_by(users_table.c.name.desc())

        :param column: A :class:`.ColumnElement` (e.g. scalar SQL expression)
         with which to apply the :func:`.desc` operation.

        .. seealso::

            :func:`.asc`

            :func:`.nullsfirst`

            :func:`.nullslast`

            :meth:`.Select.order_by`

        """
        return UnaryExpression(
            _literal_as_label_reference(column),
            modifier=operators.desc_op,
            wraps_column_expression=False)