CREATE FUNCTION does_cat_belong_to(verifiable_id INT, sought_id INT) RETURNS tinyint(1)
BEGIN
   DECLARE current_parent_id, current_id INT;
   SET current_id = verifiable_id;
   IF verifiable_id = 0 AND sought_id <> 0 THEN RETURN FALSE;
   END IF;

   WHILE current_id > 0 DO
       SET current_id = (
           SELECT category_parent_id as virtuemart_category_id 
           FROM ytgb1_virtuemart_category_categories cc
           WHERE cc.category_child_id = current_id);
       IF current_id = sought_id THEN RETURN TRUE;
       ELSEIF current_id = 0 THEN RETURN FALSE;
       END IF;
   END WHILE;
END