Ejemplo 1a, PL/pgSQL

CREATE OR REPLACE FUNCTION suma_null(INT, INT, INT)
  RETURNS INTEGER CALLED ON NULL INPUT
  LANGUAGE plpgsql AS '
    DECLARE
      acum INTEGER;
    BEGIN
      acum := 0;
      IF $1 IS NOT NULL THEN
        acum := acum + $1;
      END IF;
      IF $2 IS NOT NULL THEN
        acum := acum + $2;
      END IF;
      IF $3 IS NOT NULL THEN
        acum := acum + $3;
      END IF;
      RETURN acum;
    END;
   ';