CREATE TABLE alfa (
    id integer NOT NULL,
    c_pbl integer DEFAULT 0 NOT NULL,
    c_aut integer DEFAULT 0 NOT NULL,
    c_kwd integer DEFAULT 0 NOT NULL,
    c_prl integer DEFAULT 0 NOT NULL,
    CONSTRAINT alfa_c_art_check CHECK ((c_pbl >= 0)),
    CONSTRAINT alfa_c_aut_check CHECK ((c_aut >= 0)),
    CONSTRAINT alfa_c_jrn_check CHECK ((c_prl >= 0)),
    CONSTRAINT alfa_c_kwd_check CHECK ((c_kwd >= 0))
);


CREATE TRIGGER trg_b_iud BEFORE INSERT OR DELETE OR UPDATE ON alfa FOR EACH ROW EXECUTE PROCEDURE trg_ba_iud()

DECLARE
 _id        INT4;
BEGIN

-- Проверка наличия значения перед обновлением
IF TG_WHEN = 'BEFORE' AND TG_OP = 'UPDATE' THEN
 SELECT id FROM alfa WHERE id = NEW.id INTO _id;
 IF NOT FOUND THEN
  INSERT INTO alfa (id) VALUES (NEW.id);
 END IF;
END IF;

IF TG_OP = 'INSERT' OR TG_OP = 'UPDATE' THEN
  RETURN NEW;
ELSE
  RETURN OLD;
END IF;

END;