创建表时设置主键、唯一键、自动连续编号、默认值

1. 创建表 actor:
   
   create table actor ( id int primary key auto_increment, phone varchar(11) unique key, remark varchar(10) default "著名演员" );

   mysql> create table actor ( id int primary key auto_increment, phone varchar(11) unique key, remark varchar(10) default "著名演员" );
   Query OK, 0 rows affected (5.911 sec)
   
   mysql>
                                   

   int 是整数数据类型;
   primary key 是主键：不能有重复的值且不允许没有输入值 （ NULL );
   unique key 是唯一键：不能有重复的值且允许没有输入值;
   auto_increment 是自动连续编号;
   default 是设置默认值.


2. 向表 actor 添加 3 条记录:
   insert into actor ( phone ) values ( "18812345678" );
   insert into actor ( phone ) values ( "19912345678" );
   insert into actor ( phone ) values ( "16612345678" );

   mysql> insert into actor ( phone )  values  ( "18812345678" );
   Query OK, 1 row affected (1.150 sec)
   
   mysql> insert into actor ( phone )  values  ( "19912345678" );
   Query OK, 1 row affected (0.449 sec)
   
   mysql> insert into actor  ( phone )  values  ( "16612345678" );
   Query OK, 1 row affected (0.358 sec)
   
   mysql>
                                                  

   显示所有的记录:
   

   mysql> select * from actor;
   +----+-------------+----------+
   | id | phone       | remark   |
   +----+-------------+----------+
   |  1 | 18812345678 | 著名演员 |
   |  2 | 19912345678 | 著名演员 |
   |  3 | 16612345678 | 著名演员 |
   +----+-------------+----------+
   3 rows in set (0.010 sec)
   
   mysql>
                                   



3. 显示表 actor 的布局:
   describe actor;
   

   mysql> describe actor;
   +--------+-------------+------+-----+----------+----------------+
   | Field  | Type        | Null | Key | Default  | Extra          |
   +--------+-------------+------+-----+----------+----------------+
   | id     | int         | NO   | PRI | NULL     | auto_increment |
   | phone  | varchar(11) | YES  | UNI | NULL     |                |
   | remark | varchar(10) | YES  |     | 著名演员 |                |
   +--------+-------------+------+-----+----------+----------------+
   3 rows in set (0.022 sec)
   
   mysql>
                                   

4. 设置连续编号的初始值:
   alter table actor auto_increment=88;
   

   mysql> alter table actor  auto_increment=88;
   Query OK, 0 rows affected (3.964 sec)
   Records: 0  Duplicates: 0  Warnings: 0
   
   mysql>
                                   

   向表 actor 添加 3 条记录:
   insert into actor ( phone ) values ( "15012345678" );
   insert into actor ( phone ) values ( "15112345678" );
   insert into actor ( phone ) values ( "15212345678" );

   mysql> insert into actor ( phone )  values  ( "15012345678" );
   Query OK, 1 row affected (0.824 sec)
   
   mysql> insert into actor ( phone )  values  ( "15112345678" );
   Query OK, 1 row affected (0.826 sec)
   
   mysql> insert into actor  ( phone )  values  ( "15212345678" );
   Query OK, 1 row affected (0.260 sec)
                                                  

   显示所有的记录:
   

   mysql> select * from actor;
   +----+-------------+----------+
   | id | phone       | remark   |
   +----+-------------+----------+
   |  1 | 18812345678 | 著名演员 |
   |  2 | 19912345678 | 著名演员 |
   |  3 | 16612345678 | 著名演员 |
   | 88 | 15012345678 | 著名演员 |
   | 89 | 15112345678 | 著名演员 |
   | 90 | 15212345678 | 著名演员 |
   +----+-------------+----------+
   6 rows in set (0.007 sec)
   
   mysql>