mysql中You can't specify target table for update in FROM clause错误

mysql中You can’t specify target table for update in FROM clause错误意思你不可以对某个表现进行select，然后根据select出来的值再进行操作。比如：

update tbl t
set t.name = 'xxx'
where id in
(
select max(id) from tbl a where EXISTS
(
select 1 from tbl b where a.tac=b.tac group by xx
)
group by xx
)

解决方案是对select出来的结果进行一次包装：如下

update tbl t
set t.name = 'xxx'
where id in
(
select * from (
select max(id) from tbl a where EXISTS
(
select 1 from tbl b where a.tac=b.tac group by xx
)
group by xx
) tmp
)

这样就ok了