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

mysql中You can't specify target table <tbl> for update in FROM clause错误的意思是说，不能先select出同一表中的某些值，再update这个表(在同一语句中)。 例如下面这个sql：

delete from tbl where id in 
(
        select max(id) from tbl a where EXISTS
        (
            select 1 from tbl b where a.tac=b.tac group by tac HAVING count(1)>1
        )
        group by tac
)

改写成下面就行了：

delete from tbl where id in 
(
    select a.id from 
    (
        select max(id) id from tbl a where EXISTS
        (
            select 1 from tbl b where a.tac=b.tac group by tac HAVING count(1)>1
        )
        group by tac
    ) a
)

也就是说将select出的结果再通过中间表select一遍，这样就规避了错误。注意，这个问题只出现于mysql，mssql和oracle不会出现此问题。

例子：

delete from brand 

where brand_store_sn in(

select a.brand_store_sn from (select brand_store_sn from brand 

group by brand_store_sn

HAVING COUNT(brand_store_sn)>1) a

)

and id not in (

select a.id from (select max(id) as id from brand 

group by brand_store_sn

HAVING COUNT(brand_store_sn)>1) a

)