测试数据

-- 创建测试表1
CREATE TABLE `testtable1` (
`Id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT,
`UserId` INT(11) DEFAULT NULL,
`UserName` VARCHAR(10) DEFAULT NULL,
`UserType` INT(11) DEFAULT NULL,
PRIMARY KEY (`Id`),
UNIQUE KEY `IX_UserId` (`UserId`)
) ENGINE=INNODB DEFAULT CHARSET=utf8; -- 创建测试表2
CREATE TABLE `testtable2` (
`Id` INT(11) NULL AUTO_INCREMENT,
`UserId` INT(11) DEFAULT NULL,
`UserName` VARCHAR(10) DEFAULT NULL,
`UserType` INT(11) DEFAULT NULL,
PRIMARY KEY (`Id`),
UNIQUE KEY `IX_UserId` (`UserId`)
) ENGINE=INNODB DEFAULT CHARSET=utf8; -- 插入测试数据1
INSERT INTO testtable1(Id,UserId,UserName,UserType)
VALUES(1,101,'aa',1),(2,102,'bbb',2),(3,103,'ccc',3); -- 插入测试数据2
INSERT INTO testtable2(Id,UserId,UserName,UserType)
VALUES(1,201,'aaa',1),(2,202,'bbb',2),(3,203,'ccc',3),(4,101,'xxxx',5);

可以看到上边的数据中会有userid为重复的数据 userid=101

mysql> show tables;
+---------------+
| Tables_in_dev |
+---------------+
| testtable1    |
| testtable2    |
+---------------+
mysql> select * from testtable1;
+----+--------+----------+----------+
| Id | UserId | UserName | UserType |
+----+--------+----------+----------+
|  1 |    101 | aa       |        1 |
|  2 |    102 | bbb      |        2 |
|  3 |    103 | ccc      |        3 |
+----+--------+----------+----------+
3 rows in set (0.04 sec)mysql> select * from testtable2;
+----+--------+----------+----------+
| Id | UserId | UserName | UserType |
+----+--------+----------+----------+
|  1 |    201 | aaa      |        1 |
|  2 |    202 | bbb      |        2 |
|  3 |    203 | ccc      |        3 |
|  4 |    101 | xxxx     |        5 |
+----+--------+----------+----------+
4 rows in set (0.04 sec)### 当执行以下sql时，会报1062错误，提示有重复的key
mysql> insert into testtable1 (userid,username,usertype)-> select userid,username,usertype from testtable2;
1062 - Duplicate entry '101' for key 'IX_UserId'

• 如果想让上边的sql执行成功的话，可以使用IGNORE关键字

mysql> insert ignore into testtable1 (userid,username,usertype)-> select userid,username,usertype from testtable2;
Query OK, 3 rows affected (0.12 sec)
Records: 4  Duplicates: 1  Warnings:1
mysql> select * from testtable1;
+----+--------+----------+----------+
| Id | UserId | UserName | UserType |
+----+--------+----------+----------+
|  1 |    101 | aa       |        1 |
|  2 |    102 | bbb      |        2 |
|  3 |    103 | ccc      |        3 |
| 11 |    201 | aaa      |        1 |
| 12 |    202 | bbb      |        2 |
| 13 |    203 | ccc      |        3 |
+----+--------+----------+----------+
6 rows in set (0.05 sec)

查询sql，显示testtable2表中的数据插入到了表1中（除了重复key的那条信息）

另外注意到主键id为11,12,13开始的，这个是因为之前insert的sql失败导致的自增主键不连续

导入并覆盖重复数据，REPLACE INTO

上边那个是没有插入重复key的数据

• 回滚之前testtable1表的数据

  mysql> truncate table testtable1;
  Query OK, 0 rows affected (0.62 sec)mysql> select * from testtable1;
  Empty set
  mysql> -- 插入测试数据1
  INSERT INTO testtable1(Id,UserId,UserName,UserType)
  VALUES(1,101,'aa',1),(2,102,'bbb',2),(3,103,'ccc',3);
  Query OK, 3 rows affected (0.09 sec)
  

  mysql> replace into testtable1 (userid,username,usertype)-> select userid,username,usertype from testtable2;
  Query OK, 5 rows affected (0.10 sec)
  Records: 4  Duplicates: 1  Warnings: 0
  mysql> select * from testtable1;
  +----+--------+----------+----------+
  | Id | UserId | UserName | UserType |
  +----+--------+----------+----------+
  |  2 |    102 | bbb      |        2 |
  |  3 |    103 | ccc      |        3 |
  |  4 |    201 | aaa      |        1 |
  |  5 |    202 | bbb      |        2 |
  |  6 |    203 | ccc      |        3 |
  |  7 |    101 | xxxx     |        5 |
  +----+--------+----------+----------+
  

  可以看到表1中的101的username被覆盖为表2中的数据，这个是因为replace是现将原来表一中重复的数据删除掉，然后再执行插入新的数据

  导入重复数据，保留未指定的值

  mysql> insert into testtable1 (userid,username,usertype) -> select userid,username,usertype from testtable2-> on duplicate key update-> testtable1.username = testtable2.username;
  

  以上sql对于重复的数据，只是将username进行了覆盖，其他的值还是表一中的数据