首先創建一個表：

CREATE TABLE `t1` ( `id` INT(11) NULL DEFAULT NULL, `name` VARCHAR(20) NULL DEFAULT NULL )

插入幾條數據：

mysql> select * from t1; +------+------+ | id | name | +------+------+ | 1 | chen | | 2 | li | | 3 | huan | +------+------+ 3 rows in set (0.00 sec)

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需求1：刪除最大id的那條記錄，于是我們會大約寫出如下的語句：

mysql> delete from t1 where id=(select max(id) from t1); ERROR 1093 (HY000): You can't specify target table 't1' for update in FROM clause
很不幸，它報錯了.

可以修改成如下語句：

mysql> delete a from t1 a,(select max(id) maxid from t1) b where a.id=b.maxid; Query OK, 1 row affected (0.01 sec)mysql> select * from t1; +------+------+ | id | name | +------+------+ | 1 | chen | | 2 | li | +------+------+ 2 rows in set (0.00 sec)

也可以是如下語句：

mysql> delete from t1 where id in ( select a.maxid from (select max(id) maxid from t1) a); Query OK, 1 row affected (0.01 sec)mysql> select * from t1; +------+------+ | id | name | +------+------+ | 1 | chen | +------+------+ 1 row in set (0.00 sec)

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需求2：插入一條記錄，并且id值是之前該表最大值加1，于是我們會大約寫出如下的語句：

mysql> insert into t1 values( (select max(id)+1 from t1),'you'); ERROR 1093 (HY000): You can't specify target table 't1' for update in FROM clause
依舊報了同樣的錯誤

可以改寫如下：

mysql> insert into t1 select (select max(id)+1 maxid from t1 ) , 'you'; Query OK, 1 row affected (0.06 sec) Records: 1 Duplicates: 0 Warnings: 0mysql> select * from t1; +------+------+ | id | name | +------+------+ | 1 | chen | | 2 | you | +------+------+ 2 rows in set (0.00 sec)

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需求3：我們要更新一條語句，id需要變為之前最大值加1，于是我們會大約寫出如下的語句：?

mysql> update t1 set id=(select max(id)+1 from t1) where id=1; ERROR 1093 (HY000): You can't specify target table 't1' for update in FROM clause
錯誤如初

我們可以改寫為如下語句：

mysql> update t1,(select max(id)+1 as maxid from t1 ) a set id=a.maxid where id=1; Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from t1; +------+------+ | id | name | +------+------+ | 3 | chen | | 2 | you | +------+------+ 2 rows in set (0.00 sec)

也可以改成如下語句：

mysql> update t1 set id=(select a.maxid from (select max(id)+1 maxid from t1) a) where id=3; Query OK, 1 row affected (0.01 sec) Rows matched: 1 Changed: 1 Warnings: 0mysql> select * from t1; +------+------+ | id | name | +------+------+ | 4 | chen | | 2 | you | +------+------+ 2 rows in set (0.00 sec)

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總的思路是：把查詢的最大值語句轉為subquery或derived。

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轉載于:https://www.cnblogs.com/zejin2008/p/4974166.html

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