约束类型测试6

目的

配合整数型，主键使用自动增长约束

创建表插入数据

表company.department3

CREATE TABLE department3 (

dept_id INT PRIMARY KEY AUTO_INCREMENT,

dept_name VARCHAR(30),

comment VARCHAR(50)

);

插入数据

合法数据

mysql> insert into department3 values(1,'zs','manager');

Query OK, 1 row affected (0.01 sec)

非法数据

mysql> insert into department3 values(1,'zs','manager');

ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY'

合法数据

mysql> insert into department3 values(2,'zs','manager');

Query OK, 1 row affected (0.01 sec)

合法数据。未插入序号，但是在查询时会自动增加。

mysql> insert into department3 (dept_name,comment) values('zs','manager'');

Query OK, 1 row affected (0.01 sec)

查看信息

mysql> select * from department3;

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

| dept_id | dept_name | comment |

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

|      1 | zs        | manager |

|      2 | zs        | manager |

|      3 | zs        | manager |

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

3 rows in set (0.00 sec)