大家看看这sql语句有错误吗

本人对pl sql比较熟悉 可这个mysql 怎么更新都搞不对 看看那里错误了

update cdb_members,'uchome.uchome_member'  set cdb_members.username='uchome.uchome_member'.username where  'uchome.uchome_member'.uid=cdb_members.uid and cdb_members.uid in (select a.uid FROM `cdb_members` a, uchome.uchome_member b
WHERE a.uid = b.uid
AND a.username <> b.username
)

一开始是写成这样的  说什么错误
update cdb_members t set username=(select username from uchome.uchome_member t1 where  t.uid=t1.uid) where uid in (select a.uid FROM `cdb_members` a, uchome.uchome_member b
WHERE a.uid = b.uid
AND a.username <> b.username
)

哪位高手看看哈

没看懂，我是新手

update？。。。