mysql 约束条件 auto_increment 自动增长 修改自增字段起始值

创建一张表 t20

mysql> create table t20( id int primary key auto_increment, name char(16) );

Query OK, 0 rows affected (0.01 sec)

mysql> desc t20;

+-------+----------+------+-----+---------+----------------+

| Field | Type     | Null | Key | Default | Extra          |

+-------+----------+------+-----+---------+----------------+

| id    | int(11)  | NO   | PRI | NULL    | auto_increment |

| name  | char(16) | YES  |     | NULL    |                |

+-------+----------+------+-----+---------+----------------+

2 rows in set (0.00 sec)

修改自增字段为3 下次插入新纪录 从3开始

mysql> alter table t20 auto_increment=3;

Query OK, 0 rows affected (0.00 sec)

Records: 0  Duplicates: 0  Warnings: 0

mysql> show create  table t20\G;

*************************** 1. row ***************************

       Table: t20

Create Table: CREATE TABLE `t20` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `name` char(16) DEFAULT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

插入记录

mysql> insert into t20(name) values('mike');

Query OK, 1 row affected (0.00 sec)

mysql> select * from t20;

+----+------+

| id | name |

+----+------+

|  3 | mike |

+----+------+

1 row in set (0.00 sec)

mysql> show create  table t20\G;

*************************** 1. row ***************************

       Table: t20

Create Table: CREATE TABLE `t20` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `name` char(16) DEFAULT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8

1 row in set (0.00 sec)