在MySql中,这四种方法可以避免重复插入数据!
insert ignore。 replace into insert on duplicate key update
insert ignore
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=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)
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
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
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)
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)
insert on duplicate key 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)
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)
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