BEGIN  IF (in_drop_value IS NULL) THEN SIGNAL SQLSTATE '02200' SET MESSAGE_TEXT = 'Function sys.list_drop: in_drop_value input variable should not be NULL', MYSQL_ERRNO = 1138; END IF;  IF (in_list IS NULL OR LENGTH(in_list) = 0) THEN RETURN in_list; END IF;  RETURN (SELECT TRIM(BOTH ',' FROM REPLACE(REPLACE(CONCAT(',', in_list), CONCAT(',', in_drop_value), ''), CONCAT(', ', in_drop_value), '')));  END