前言

MySql 在存在主鍵沖突或唯一鍵沖突的情況下，根據插入方式，一般有以下三種插入方式避免錯誤。

insert ignore

insert ignore 會忽視數據庫中已經存在的數據，根據主鍵或者唯一索引判斷，如果數據庫沒有數據，就會插入新的數據，如果有數據的話就跳過這條數據

小case

表結構

root:test> show create table t3G*************************** 1. row *************************** Table: t3Create Table: CREATE TABLE `t3` ( `id` int(11) NOT NULL AUTO_INCREMENT, `c1` int(11) DEFAULT NULL, `c2` varchar(20) DEFAULT NULL, `c3` int(11) DEFAULT NULL, PRIMARY KEY (`id`), UNIQUE KEY `uidx_c1` (`c1`)) ENGINE=InnoDB AUTO_INCREMENT=18 DEFAULT CHARSET=utf81 row in set (0.00 sec)root:test> select * from t3; +----+------+------+------+ | id | c1 | c2 | c3 | +----+------+------+------+ | 1 | 1 | a | 1 | | 2 | 2 | a | 1 | | 8 | NULL | NULL | 1 | | 14 | 4 | bb | NULL | | 17 | 5 | cc | 4 | +----+------+------+------+ 5 rows in set (0.00 sec)

插入沖突數據

root:test> insert ignore into t3 (c1,c2,c3) values(5,’cc’,4),(6,’dd’,5); Query OK, 1 row affected, 1 warning (0.01 sec)Records: 2 Duplicates: 1 Warnings: 1

查看結果

root:test> show warnings;+---------+------+---------------------------------------+| Level | Code | Message|+---------+------+---------------------------------------+| Warning | 1062 | Duplicate entry ’5’ for key ’uidx_c1’ |+---------+------+---------------------------------------+1 row in set (0.00 sec)root:test> select * from t3;+----+------+------+------+| id | c1 | c2 | c3 |+----+------+------+------+| 1 | 1 | a | 1 || 2 | 2 | a | 1 || 8 | NULL | NULL | 1 || 14 | 4 | bb | NULL || 17 | 5 | cc | 4 || 18 | 6 | dd | 5 |+----+------+------+------+6 rows in set (0.00 sec)

replace into

replace into 會嘗試先插入數據，如果發現沖突進行刪除。否則不做任何操作。

小case

root:test> show create table t3G*************************** 1. row *************************** Table: t3Create Table: CREATE TABLE `t3` ( `id` int(11) NOT NULL AUTO_INCREMENT, `c1` int(11) DEFAULT NULL, `c2` varchar(20) DEFAULT NULL, `c3` int(11) DEFAULT NULL, PRIMARY KEY (`id`), UNIQUE KEY `uidx_c1` (`c1`)) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf81 row in set (0.00 sec)root:test> select * from t3;+----+------+--------+------+| id | c1 | c2 | c3 |+----+------+--------+------+| 1 | 1 | cc | 4 || 2 | 2 | dd | 5 || 3 | 3 | qwewqe | 3 |+----+------+--------+------+3 rows in set (0.00 sec)

插入沖突數據

root:test> replace into t3 (c1,c2,c3) values(3,’new’,8);Query OK, 2 rows affected (0.02 sec)root:test> select * from t3;+----+------+------+------+| id | c1 | c2 | c3 |+----+------+------+------+| 1 | 1 | cc | 4 || 2 | 2 | dd | 5 || 4 | 3 | new | 8 |+----+------+------+------+3 rows in set (0.00 sec)

可以看到原有的記錄已經沒有了，新的記錄又有了。

insert on duplicate key update

如果在insert into 語句末尾指定了 insert on duplicate key update 如果出現了重復值，則會在出現重復值以后進行update。

case

root:test> show create table t3G*************************** 1. row *************************** Table: t3Create Table: CREATE TABLE `t3` ( `id` int(11) NOT NULL AUTO_INCREMENT, `c1` int(11) DEFAULT NULL, `c2` varchar(20) DEFAULT NULL, `c3` int(11) DEFAULT NULL, PRIMARY KEY (`id`), UNIQUE KEY `uidx_c1` (`c1`)) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf81 row in set (0.00 sec)root:test> select * from t3; +----+------+------+------+| id | c1 | c2 | c3 |+----+------+------+------+| 1 | 1 | fds | 4 || 2 | 2 | ytu | 3 || 3 | 3 | czx | 5 |+----+------+------+------+3 rows in set (0.00 sec)

插入一條與記錄id=3存在唯一鍵（列c1）沖突的數據

root:test> insert into t3(c1,c2,c3) values (3,’new’,5) on duplicate key update c1=c1+3; Query OK, 2 rows affected (0.01 sec)root:test> select * from t3;+----+------+------+------+| id | c1 | c2 | c3 |+----+------+------+------+| 1 | 1 | fds | 4 || 2 | 2 | ytu | 3 || 3 | 6 | czx | 5 |+----+------+------+------+3 rows in set (0.00 sec)

可以看到，id=3的記錄發生了改變，c1=原有的c1+3,其他列沒有改變。

以上就是MySql四種避免重復插入數據的方法的詳細內容，更多關于MySQL 避免插入重復數據的資料請關注好吧啦網其它相關文章！