ction!';
    END IF;
    RETURN NULL;
END;
$$
LANGUAGE plpgsql;
</pre><p>

         The trigger definition is the same as before.
         Note that each <code class="literal">IF</code> test must exactly match the
         <code class="literal">CHECK</code> constraint for its child table.
        </p><p>
         While this function is more complex than the single-month case,
         it doesn't need to be updated as often, since branches can be
         added in advance of being needed.
        </p><div cl