mysql中You can't specify target table for update in FROM clause錯(cuò)誤的意思是說，不能先select出同一表中的某些值，再update這個(gè)表(在同一語(yǔ)句中)。 例如下面這個(gè)sql：
復(fù)制代碼 代碼如下:
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：
復(fù)制代碼 代碼如下:
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
)
也就是說將select出的結(jié)果再通過中間表select一遍，這樣就規(guī)避了錯(cuò)誤。注意，這個(gè)問題只出現(xiàn)于mysql，mssql和oracle不會(huì)出現(xiàn)此問題。
