7,mysql视图
视图是从数据库中的一个或多个表中导出来的虚拟表，起作用是方便用户对数据的操作。视图是存储在数据库汇总的查询的sql语句
1，创建视图
[*]mysql> create view
[*] -> user_view(username,password)
[*] -> as select username,password from user
[*] -> ;
[*]Query OK, 0 rows affected (0.09 sec)
2，修改视图
[*]mysql> create or replace view user_view(username) as select username from user;
[*]Query OK, 0 rows affected (0.19 sec)
[*]
[*]mysql> desc user_view;
[*]+----------+-------------+------+-----+---------+-------+
[*]| Field | Type | Null | Key | Default | Extra |
[*]+----------+-------------+------+-----+---------+-------+
[*]| username | varchar(50) | NO | | NULL | |
[*]+----------+-------------+------+-----+---------+-------+
[*]1 row in set (0.05 sec)
第一句修改了user_view视图
第二句查看user_view的结构，跟查看表结构一样
3,操作视图的时候，就是在操作一个表格，可以把视图当做表处理
[*]mysql> insert into user_view values('1','1');
[*]Query OK, 1 row affected (0.06 sec)
[*]
[*]mysql> select * from user_view;
[*]+----------+----------+
[*]| username | password |
[*]+----------+----------+
[*]| kenan | kenan |
[*]| kenan | lele |
[*]| lele | lele |
[*]| 1 | 1 |
[*]+----------+----------+
[*]4 rows in set (0.00 sec)
[*]
[*]mysql> select * from user;
[*]+----+----------+----------+---------------------+
[*]| id | username | password | createtime |
[*]+----+----------+----------+---------------------+
[*]|1 | kenan | kenan | 2012-10-31 15:32:26 |
[*]|3 | kenan | lele | 2012-10-31 15:32:26 |
[*]|4 | lele | lele | NULL |
[*]|5 | 1 | 1 | NULL |
[*]+----+----------+----------+---------------------+
[*]4 rows in set (0.00 sec)
当对视图进行插入操作的时候，就是对实体表进行插入操作
4,删除视图
[*]mysql> drop view if exists user_view;
[*]Query OK, 0 rows affected (0.00 sec)
[*]
[*]mysql> desc user_view;
[*]ERROR 1146 (42S02): Table 'test.user_view' doesn't exist
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