是否必须将PRIMARY KEY设置为AUTO_INCREMENT值？
是的，将AUTO_INCREMENT与PRIMARYKEY一起使用。让我们首先创建一个表-
mysql> create table DemoTable ( EmployeeId int NOT NULL AUTO_INCREMENT, EmployeeName varchar(40), EmployeeAge int, PRIMARY KEY(EmployeeId), UNIQUE KEY(EmployeeName,EmployeeAge) );
让我们检查表的表说明-
mysql> desc DemoTable;
这将产生以下输出-
+--------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+-------------+------+-----+---------+----------------+ | EmployeeId | int(11) | NO | PRI | NULL | auto_increment | | EmployeeName | varchar(40) | YES | MUL | NULL | | | EmployeeAge | int(11) | YES | | NULL | | +--------------+-------------+------+-----+---------+----------------+ 3 rows in set (0.17 sec)
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable(EmployeeName,EmployeeAge) values('Chris',25);
mysql> insert into DemoTable(EmployeeName,EmployeeAge) values('Robert',34);
mysql> insert into DemoTable(EmployeeName,EmployeeAge) values('Mike',32);使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
这将产生以下输出-
+------------+--------------+-------------+ | EmployeeId | EmployeeName | EmployeeAge | +------------+--------------+-------------+ | 1 | Chris | 25 | | 3 | Mike | 32 | | 2 | Robert | 34 | +------------+--------------+-------------+ 3 rows in set (0.00 sec)