树表更新分支最大级数的问题
现在有这么个树表
create table MENU_INFO
(
ID NUMBER(9) not null,--序号
MENU VARCHAR2(40) not null,--菜单编码
MENU_NAME VARCHAR2(40),--菜单名称
FATHER_MENU VARCHAR2(40),--父菜单编码
STEP NUMBER(9),--菜单级数
MAX_STEP NUMBER(9)--该分支最大级数
)
现在我已经写出更新STEP列的SQL语句:
update menu_info b
set step = (select a.nstep
from (select id, step, (level - 1) nstep
from menu_info
start with father_menu = '0'
connect by father_menu = prior menu) a
where a.id = b.id);
请问怎么写更新MAX_STEP列的SQL语句?