Is there another answer, asside from in the application and/or as a trigger using `DELETE FROM B WHERE z = 'x';` as it's body?
CREATE TABLE order_items ( product_no integer REFERENCES products ON DELETE RESTRICT, order_id integer REFERENCES orders ON DELETE CASCADE, quantity integer, PRIMARY KEY (product_no, order_id)
pgsql-sql by date:
Соглашаюсь с условиями обработки персональных данных