PostgreSQL function returning multiple result sets

Question

Is it possible to return multiple result sets from a Postgres function, like in MSSQL:

CREATE PROCEDURE test

AS

SELECT * FROM first_table

SELECT * FROM second_table

Answer 1

A simpler way has been around since PostgreSQL 8.3:

CREATE FUNCTION test()
  RETURNS SETOF first_table AS
$func$
BEGIN

RETURN QUERY
SELECT * FROM first_table;

RETURN QUERY
SELECT * FROM second_table;   -- has to return same rowtype as first_table!

END
$func$ LANGUAGE plpgsql;

Call:

SELECT * FROM test();

Both result sets are appended to a single set returned from the function.
See the manual for RETURN QUERY.