mysql 的delete from 和update子查詢限制

最經作項目時發現的問題，好像在update時也有。。。

 

網上查到的資料以下：

 

1.使用mysql進行delete from操做時，若子查詢的 FROM 字句和更新/刪除對象使用同一張表，會出現錯誤。 

mysql> DELETE FROM tab1 WHERE col1 = ( SELECT MAX( col1 ) FROM tab1 ); 
ERROR 1093 (HY000): You can’t specify target table ‘tab1′ for update in FROM clause 

針對「同一張表」這個限制，撇開效率不談，多數狀況下均可以經過多加一層select 別名表來變通解決，像這樣 

DELETE FROM tab1 
WHERE col1 = ( 
SELECT MAX( col1 ) 
FROM ( 
SELECT * FROM tab1 
) AS t 
); 
或這樣

delete from theTable where id in
(
select id from
(
select min(id) id from theTable group by title HAVING count(*)>1
) ids
) ;

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2. mysql delete from where in 時後面 的查詢語句裏不能加where條件 


Sql代碼 
      delete from `t_goods` where fi_id in (select * from ( select fi_id from `t_goods` where fs_num is null and fs_name is null and fs_type is null and fs_using is null and fs_lifetime is null) b)  


Sql代碼 
      delete from `t_goods` where fi_id in (select fi_id from `t_goods` where fs_num is null and fs_name is null and fs_type is null and fs_using is null and fs_lifetime is null)   


Sql代碼 
      delete from `t_goods` where fi_id in ( select fi_id from `t_goods` )   

上面三種狀況，只有中間的不能執行。 

綜合起來就是mysql delete from where in 時後面 的查詢語句裏不能加where條件 

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3. delete from table... 這其中table不能使用別名 

Sql代碼 

    delete from student a where a.id in (1,2);(執行失敗) 

    

     select a.* from student a where a.id in (1,2);(執行成功)