MySQL: [Err] 1093 - You can't specify target table 'bk' for update in FROM clause

標籤：

  錯誤的意思說，不能先select出同一表中的某些值，再update這個表(在同一語句中)。 例如下面這個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
)

 

 

改寫成下面就行了：

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
)

 

再如：UPDATE bk_ygsbk AS bk SET REPORT_VISIT = ( SELECT COUNT(*) FROM bk_ygsbk WHERE ZYID = ‘1‘ )  WHERE bk.ZYID = ‘1‘  

應改成：UPDATE bk_ygsbk AS bk SET REPORT_VISIT = (SELECT * FROM ( SELECT COUNT(*) FROM bk_ygsbk WHERE ZYID = ‘1‘ ) AS r ) WHERE bk.ZYID = ‘1‘

 

也就是說將select出的結果再通過中間表select一遍，這樣就規避了錯誤。注意，這個問題只出現於mysql，mssql和oracle不會出現此問題。

MySQL: [Err] 1093 - You can't specify target table 'bk' for update in FROM clause