更新时间:2023-04-19 GMT+08:00
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修改表的自增AUTO_INCREMENT值

修改方法如下:

  • 当AUTO_INCREMENT大于表中数据的最大值时,可以在取值范围内任意修改为更大的值。
    mysql> show create table animals; 
    +---------+------------------------------------------------------------------+ 
    | Table   | Create Table                                                     | 
    +---------+------------------------------------------------------------------+ 
    | animals | CREATE TABLE `animals` (   
    `id` mediumint NOT NULL AUTO_INCREMENT,   `name` char(30) NOT NULL,   
    PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=101 DEFAULT CHARSET=utf8   | 
    +---------+------------------------------------------------------------------+ 
    1 row in set (0.00 sec)  
    mysql> select * from animals; 
    +-----+-----------+ 
    | id  | name      | 
    +-----+-----------+ 
    | -50 | -middle   | 
    |   1 | fish       | 
    |   2 | cat       | 
    |  50 | middle    | 
    | 100 | rabbit    | 
    +-----+-----------+ 
    11 rows in set (0.00 sec)  
    mysql> alter table animals AUTO_INCREMENT=200; 
    Query OK, 0 rows affected (0.22 sec) 
    Records: 0  Duplicates: 0  Warnings: 0  
    mysql> show create table animals; 
    +---------+-------------------------------------------------------+ 
    | Table   | Create Table                                          | 
    +---------+-------------------------------------------------------+ 
    | animals | CREATE TABLE `animals` (   
    `id` mediumint NOT NULL AUTO_INCREMENT,   `name` char(30) NOT NULL,   
    PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=200 DEFAULT CHARSET=utf8 | 
    +---------+-------------------------------------------------------+
  • 当AUTO_INCREMENT大于表中数据的最大值时,如果修改后的指定值仍大于数据的最大值,则修改为指定值成功。否则,默认会修改为数据最大值+1。
    mysql> select * from animals; 
    +-----+-----------+ 
    | id  | name      | 
    +-----+-----------+ 
    | -50 | -middle   | 
    |   1 | fish       | 
    |   2 | cat       | 
    |  50 | middle    | 
    | 100 | rabbit    | 
    +-----+-----------+ 
    mysql> show create table animals; 
    +---------+-----------------------------------------------------+ 
    | Table   | Create Table                                        | 
    +---------+-----------------------------------------------------+ 
    | animals | CREATE TABLE `animals` (   
    `id` mediumint NOT NULL AUTO_INCREMENT,   `name` char(30) NOT NULL,   
    PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=200 DEFAULT CHARSET=utf8 | 
    +---------+-----------------------------------------------------+ 
    mysql> alter table animals AUTO_INCREMENT=150; 
    Query OK, 0 rows affected (0.05 sec) 
    Records: 0  Duplicates: 0  Warnings: 0 
    mysql> show create table animals; 
    +---------+-----------------------------------------------------+ 
    | Table   | Create Table                                         | 
    +---------+-----------------------------------------------------+ 
    | animals | CREATE TABLE `animals` (   
    `id` mediumint NOT NULL AUTO_INCREMENT,   `name` char(30) NOT NULL,   
    PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=150 DEFAULT CHARSET=utf8 | 
    +---------+-----------------------------------------------------+ 
    mysql> alter table animals AUTO_INCREMENT=50; 
    Query OK, 0 rows affected (0.04 sec) 
    Records: 0  Duplicates: 0  Warnings: 0 
    mysql> show create table animals; 
    +---------+-----------------------------------------------------+ 
    | Table   | Create Table                                        | 
    +---------+-----------------------------------------------------+ 
    | animals | CREATE TABLE `animals` (   
    `id` mediumint NOT NULL AUTO_INCREMENT,   `name` char(30) NOT NULL,   
    PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=101 DEFAULT CHARSET=utf8 | 
    +---------+-----------------------------------------------------+ 
    mysql> delete from animals where id=100; 
    Query OK, 1 row affected (0.00 sec)  
    mysql> select * from animals; 
    +-----+-----------+ 
    | id  | name      | 
    +-----+-----------+ 
    | -50 | -middle   | 
    |   1 | fish       | 
    |   2 | cat       | 
    |  50 | middle    | 
    +-----+-----------+ 
    10 rows in set (0.00 sec)  
    mysql> alter table animals AUTO_INCREMENT=50; 
    Query OK, 0 rows affected (0.04 sec) 
    Records: 0  Duplicates: 0  Warnings: 0  
    mysql> show create table animals; 
    +---------+-----------------------------------------------------+ 
    | Table   | Create Table                                        | 
    +---------+-----------------------------------------------------+ 
    | animals | CREATE TABLE `animals` (   
    `id` mediumint NOT NULL AUTO_INCREMENT,   `name` char(30) NOT NULL,   
    PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=51 DEFAULT CHARSET=utf8 | 
    +---------+-----------------------------------------------------+ 
    1 row in set (0.00 sec)
  • AUTO_INCREMENT无法修改为负数。
    mysql> alter table animals AUTO_INCREMENT=-1; 
    ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '-1' at line 1

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