最近几天，产品上线比较多，从内网测试库导出表的部分内容到线上也就比平时频繁多了，这时候可能会出现主键冲突：

Error Code : 1062

Duplicate entry '1' for key 'PRIMARY'

总结下，三种解决方案来避免出错

1.insert ignore into

遇主键冲突，保持原纪录

mysql> select * from device ;

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

| devid | status | spec_char

|

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

|

1 | dead   | zhonghuaren |

|

2 | dead   |

zhong

|

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

2 rows in set (0.00 sec)

mysql> insert into device values

(1,'alive','yangting');

ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY'

mysql> insert ignore  into device

values (1,'alive','yangting');

Query OK, 0 rows affected (0.00 sec)

mysql> select * from device ;

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

| devid | status | spec_char

|

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

|

1 | dead   | zhonghuaren |

|

2 | dead   |

zhong

|

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

2 rows in set (0.00 sec)

可见 insert ignore

into当遇到主键冲突时，不跟改原纪录，也不报错

2：REPLACE into

遇主键冲突，替换原纪录，即

先删除原纪录，后insert 新纪录

mysql> replace  into device values

(1,'alive','yangting');

Query OK, 2 rows affected (0.00 sec)

mysql> select * from device ;

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

| devid | status | spec_char |

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

|

1 | alive  | yangting  |

|

2 | dead   |

zhong

|

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

2 rows in set (0.00 sec)

3：INSERT ... ON DUPLICATE KEY UPDATE

其实这个是原本需要执行3条SQL语句(SELECT,INSERT,UPDATE)，缩减为1条语句即可完成。

即

IF (SELECT * FROM where 存在) {

UPDATE  SET  WHERE ;

} else {

INSERT INTO;

}

如：mysql> insert into device values

(1,'readonly','yang') ON DUPLICATE KEY UPDATE status

='drain';

Query OK, 2 rows affected (0.00 sec)

上面语句伪代码表示即为

if (select * from device where devid=1)

{ update device set status ='drain' where devid=1

}else {insert into device values (1,'readonly','yang')}

很明显，devid=1

是有的，这样就执行update操作

mysql> select * from device ;

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

| devid | status | spec_char |

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

|

1 | drain  | yangting  |

|

2 | dead   |

zhong

|

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

2 rows in set (0.00 sec)

测试表：

CREATE TABLE `device` (

`devid` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,

`status` enum('alive','dead','down','readonly','drain') DEFAULT

NULL,

`spec_char` varchar(11) DEFAULT '0',

PRIMARY KEY (`devid`)

) ENGINE=InnoDB