sql上下级关系查询

create table menu 
(
   id                   int             not null,
   menucode              varchar(100),
   menuname              varchar(100),
   linkadress           varchar(500),
   parentId                char(100) null,
   constraint PK_menu primary key (id)
);

SELECT a.*,rowid FROM menu a

SELECT a.*, rowid
  FROM menu a
        SELECT parentId,
               wm_concat(id),
               wm_concat(menuname),
               wm_concat(linkadress)
          FROM menu
         group by parentid