前言
MySql 在存在主鍵沖突或唯一鍵沖突的情況下，根據(jù)插入方式，一般有以下三種插入方式避免錯(cuò)誤。
- insert ignore。
- replace into
- insert on duplicate key update
insert ignore
insert ignore 會(huì)忽視數(shù)據(jù)庫中已經(jīng)存在的數(shù)據(jù)，根據(jù)主鍵或者唯一索引判斷，如果數(shù)據(jù)庫沒有數(shù)據(jù)，就會(huì)插入新的數(shù)據(jù)，如果有數(shù)據(jù)的話就跳過這條數(shù)據(jù)
小case
表結(jié)構(gòu)
root:test> show create table t3G
*************************** 1. row ***************************
Table: t3
Create 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=utf8
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 |
+----+------+------+------+
5 rows in set (0.00 sec)
插入沖突數(shù)據(jù)
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(jié)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(huì)嘗試先插入數(shù)據(jù)，如果發(fā)現(xiàn)沖突進(jìn)行刪除。否則不做任何操作。
小case
root:test> show create table t3G
*************************** 1. row ***************************
Table: t3
Create 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=utf8
1 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(shù)據(jù)
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(jīng)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(xiàn)了重復(fù)值，則會(huì)在出現(xiàn)重復(fù)值以后進(jìn)行update。
case
root:test> show create table t3G
*************************** 1. row ***************************
Table: t3
Create 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=utf8
1 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(shù)據(jù)
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(fā)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(fù)插入數(shù)據(jù)的方法的詳細(xì)內(nèi)容，更多關(guān)于MySQL 避免插入重復(fù)數(shù)據(jù)的資料請關(guān)注腳本之家其它相關(guān)文章！
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