第一部分:初级概念及应用
一,视图简介
MySQL的视图和Oracle视图是一个概念,就是一张虚拟表,没有任何数据的,数据还是存放在基表里面的;
二,添加视图1:语法
CREATE
[OR REPLACE]
[ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
[DEFINER = { user | CURRENT_USER }]
[SQL SECURITY { DEFINER | INVOKER }]
VIEW view_name [(column_list)]
AS select_statement
[WITH [CASCADED | LOCAL] CHECK OPTION]
2:举例(创建视图 )
mysql> use ehrt;
Database changed
mysql> create algorithm = MERGE view t1 as select * from user;
三,修改视图
1:语法
ALTER
[ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
[DEFINER = { user | CURRENT_USER }]
[SQL SECURITY { DEFINER | INVOKER }]
VIEW view_name [(column_list)]
AS select_statement
[WITH [CASCADED | LOCAL] CHECK OPTION]
2:举例
mysql> alter view t1 as select * from user where name='Jacson';
四,查看视图
1.查看视图数据
mysql> use ehrt;mysql> select * from t1;
+----+------+-----+
| id | name | sex |
+----+------+-----+
| 1 | Jacson | 0 |
| 2 | Bai | 0 |
+----+------+-----+
2 rows in set (0.00 sec)
2.查看视图结构
mysql> show create view t1G;五,删除视图
mysql> drop view t1;
Query OK, 0 rows affected (0.00 sec)
第二部分:高级概念整理
一,视图的类型
mysql的视图有三种类型:MERGE、TEMPTABLE、UNDEFINED。如果不指定ALGORITHM子句,默认算法为UNDEFINED。这个方式决定了影响MySQL处理视图的速度。
1,MERGE,会将引用视图的语句的文本与视图定义合并起来,使得视图定义的某一部分取代语句的对应部分。
2,TEMPTABLE,视图的结果将被置于临时表中,然后使用它执行语句。
3,UNDEFINED,让自己MySQL选择所要使用的算法。
建议一般开发者,在物理主机内存不大或者考虑程序可移植的情况下一般选择MERGE
--未完待续
第三部分:高级应用
1.能否监控视图是否失效?
--未完待续

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