對于這個錯誤信息：

ERROR 1093 (HY000): You can't specify target table 'clients' for update in FROM clause

或者：

ERROR 1093 (HY000): You can't specify target table 'clients' for delete in FROM clause

一直以來我以為只有一種辦法。不過今天翻開以前的書，發現還有一個方法。

表結構和示例數據：

mysql> show create table branches\G

*************************** 1. row ***************************

?????? Table: branches

Create Table: CREATE TABLE `branches` (

? `bid` int(11) NOT NULL,

? `cid` int(11) NOT NULL,

? `bdesc` varchar(1000) NOT NULL,

? `bloc` char(2) NOT NULL,

? PRIMARY KEY (`bid`),

? KEY `cid` (`cid`),

? CONSTRAINT `branches_ibfk_1` FOREIGN KEY (`cid`) REFERENCES `clients` (`cid`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

mysql> select * from branches;

+------+-----+--------------------------------+------+

| bid? | cid | bdesc????????????????????????? | bloc |

+------+-----+--------------------------------+------+

| 1011 | 101 | Corporate HQ?????????????????? | CA?? |

| 1012 | 101 | Accounting Department????????? | NY?? |

| 1013 | 101 | Customer Grievances Department | KA?? |

| 1031 | 103 | N Region HO??????????????????? | ME?? |

| 1032 | 103 | NE Region HO?????????????????? | CT?? |

| 1033 | 103 | NW Region HO?????????????????? | NY?? |

| 1041 | 104 | Branch Office (East)?????????? | MA?? |

| 1042 | 104 | Branch Office (West)?????????? | CA?? |

| 1101 | 110 | Head Office??????????????????? | CA?? |

+------+-----+--------------------------------+------+

9 rows in set (0.00 sec)

mysql> show create table clients\G

*************************** 1. row ***************************

?????? Table: clients

Create Table: CREATE TABLE `clients` (

? `cid` int(11) NOT NULL,

? `cname` varchar(64) NOT NULL,

? PRIMARY KEY (`cid`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

mysql> select * from clients;

+-----+-----------------------------+

| cid | cname?????????????????????? |

+-----+-----------------------------+

| 101 | JV Real Estate????????????? |

| 102 | ABC Talent Agency?????????? |

| 103 | DMW Trading???????????????? |

| 104 | Rabbit Foods Inc??????????? |

| 110 | Sharp Eyes Detective Agency |

+-----+-----------------------------+

5 rows in set (0.00 sec)

mysql> delete from clients where cid = (select clients.cid from clients left join branches using(cid) where bid is null);

ERROR 1093 (HY000): You can't specify target table 'clients' for update in FROM

clause

解決辦法

1、利用變量賦值。

mysql> select @m_cid:=clients.cid from clients left join branches using(cid) where bid is null;

+---------------------+

| @m_cid:=clients.cid |

+---------------------+

|???????????????? 102 |

+---------------------+

1 row in set (0.00 sec)

mysql> delete from clients where cid = 102;

Query OK, 1 row affected (0.05 sec)

mysql> select * from clients;

+-----+-----------------------------+

| cid | cname?????????????????????? |

+-----+-----------------------------+

| 101 | JV Real Estate????????????? |

| 103 | DMW Trading???????????????? |

| 104 | Rabbit Foods Inc??????????? |

| 110 | Sharp Eyes Detective Agency |

+-----+-----------------------------+

4 rows in set (0.00 sec)

2、用EXISTS關鍵字和相關子查詢：（不過這個沒有之前的效率高）

mysql> insert into clients values(102,'ABC Talent Agency');

Query OK, 1 row affected (0.05 sec)

mysql> delete from clients where not exists

??? -> (

??? -> select * from branches where branches.cid = clients.cid

??? -> );

Query OK, 1 row affected (0.06 sec)

mysql> select * from clients;

+-----+-----------------------------+

| cid | cname?????????????????????? |

+-----+-----------------------------+

| 101 | JV Real Estate????????????? |

| 103 | DMW Trading???????????????? |

| 104 | Rabbit Foods Inc??????????? |

| 110 | Sharp Eyes Detective Agency |

+-----+-----------------------------+

4 rows in set (0.00 sec)

轉載于:https://blog.51cto.com/wyfirst/195882

超強干貨來襲 云風專訪：近40年碼齡，通宵達旦的技術人生

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