--DROP FUNCTION IF EXISTS "provjera_kolicine" () CASCADE;

CREATE OR REPLACE FUNCTION "provjera_kolicine" ()
RETURNS TRIGGER AS
$BODY$
DECLARE
red RECORD;
BEGIN
SELECT * INTO red FROM proizvodi
WHERE NEW.proizvod_id = proizvodi.proizvod_id;

IF found THEN
IF red.kolicina < NEW.kolicina THEN
RAISE EXCEPTION 'Nema toliko';
END IF;
UPDATE proizvodi  SET kolicina = kolicina - NEW.kolicina
WHERE proizvod_id = NEW.proizvod_id;

END IF;

RETURN NEW;
END;
$BODY$
    LANGUAGE PLpgSQL
    CALLED ON NULL INPUT
    VOLATILE
    EXTERNAL SECURITY DEFINER;