create or replace TRIGGER Populate_specialite
AFTER UPDATE OR INSERT OR DELETE ON professeurs
FOR EACH ROW

BEGIN

IF inserting THEN
    UPDATE prof_specialite SET nb_professeurs = nb_professeurs + 1 WHERE specialite = :NEW.specialite;
END IF;
IF deleting THEN
    UPDATE prof_specialite SET nb_professeurs = nb_professeurs - 1 WHERE specialite = :NEW.specialite;
END IF;
IF updating THEN
    UPDATE prof_specialite SET nb_professeurs = nb_professeurs + 1 WHERE specialite = :NEW.specialite;
    UPDATE prof_specialite SET nb_professeurs = nb_professeurs - 1 WHERE specialite = :OLD.specialite;
END IF;

END;