Module « sqlalchemy »

Fonction nulls_first - module sqlalchemy

Signature de la fonction nulls_first

def nulls_first(column) 

Description

nulls_first.__doc__

Produce the ``NULLS FIRST`` modifier for an ``ORDER BY`` expression.

        :func:`.nulls_first` is intended to modify the expression produced
        by :func:`.asc` or :func:`.desc`, and indicates how NULL values
        should be handled when they are encountered during ordering::


            from sqlalchemy import desc, nulls_first

            stmt = select(users_table).order_by(
                nulls_first(desc(users_table.c.name)))

        The SQL expression from the above would resemble::

            SELECT id, name FROM user ORDER BY name DESC NULLS FIRST

        Like :func:`.asc` and :func:`.desc`, :func:`.nulls_first` is typically
        invoked from the column expression itself using
        :meth:`_expression.ColumnElement.nulls_first`,
        rather than as its standalone
        function version, as in::

            stmt = select(users_table).order_by(
                users_table.c.name.desc().nulls_first())

        .. versionchanged:: 1.4 :func:`.nulls_first` is renamed from
            :func:`.nullsfirst` in previous releases.
            The previous name remains available for backwards compatibility.

        .. seealso::

            :func:`.asc`

            :func:`.desc`

            :func:`.nulls_last`

            :meth:`_expression.Select.order_by`