SOURCE
create or replace TRIGGER t_parents_etudiants
BEFORE INSERT OR UPDATE ON parents_etudiants
FOR EACH ROW
DECLARE
compte number;
groupe_impossible EXCEPTION;
BEGIN
SELECT COUNT(g.p_id)
INTO compte
FROM groupes g, groupes_parentes gp, groupes apprenant, types_groupes tg
WHERE g.p_id = :new.pf_groupe
AND gp.pf_fils = g.p_id
AND apprenant.p_id = gp.pf_pere
AND tg.p_id = apprenant.f_type
AND tg.libelle = 'apprenant';
IF (compte != 1)
THEN
	RAISE groupe_impossible;
END IF;
END;