<para>

Here is an example of a function using <command>RETURN

QUERY</command>:

<programlisting>

CREATE FUNCTION get_available_flightid(date) RETURNS SETOF integer AS

$BODY$

BEGIN

RETURN QUERY SELECT flightid

FROM flight

WHERE flightdate >= $1

AND flightdate < ($1 + 1);

-- Since execution is not finished, we can check whether rows were returned

-- and raise exception if not.

IF NOT FOUND THEN

RAISE EXCEPTION 'No flight at %.', $1;

END IF;

RETURN;

END

$BODY$

LANGUAGE plpgsql;

-- Returns available flights or raises exception if there are no

-- available flights.

SELECT * FROM get_available_flightid(CURRENT_DATE);

</programlisting>

</para>