Ejemplo 1: Una fila, SQL

CREATE FUNCTION suma(INTEGER, INTEGER)
   RETURNS INTEGER
   IMMUTABLE
   STRICT
   LANGUAGE SQL
   AS 'SELECT $1 + $2';

regression=> select suma(10, 14);
 suma
------
   24
(1 row)

regression=> select * FROM suma(10, 14);
 suma
------
   24
(1 row)