MySql 不允许对同一张表来查询并update的。
如下面的ＳＱＬ则不能运行。
update thb As outer_thb
set cnt=(
select count(*) from thb as innter_thb
where innter_thb.type=outer_thb.type);
可以通过inner方式来达到这个目的，如下所示。
update
thb inner join (
select count(*) as cnt from thb
group by thb.type ) as inner_thb USING (type)
set thb.cnt=inner_thb. cnt;
Update XXX set XXX where 这种写法大家都知道，
这里update和delete支持inner join的update 的定法
update tb_User
set pass=''
from tb_User usr
inner join tb_Address addr on usr.nAddressFK = addr.nAddressID
where usr.id=123
update的格式是
update t1 set t1.name=’Liu’ from t1 inner join t2 on t1.id = t2.tid
delete 语句也是类似
delete from t1 from t1 inner join t2 on t1.id = t2.tid