视图的操作:
1.视图的创建:
create view view_name as 查询语句;
2.视图的查看:
show tables;// 显示所有的表和视图
show create view view_name;
desc view_name;
show table status from table_name like 'view_name';
3.使用视图(与查询表的语句相似);
select * from view_name (where 条件);
4.视图的修改:
alter view view_name as 查询语句;
create or replace view view_name as 查询语句;
5.视图的删除:
drop view view_name;
6.视图的分类:
(1).常量视图:
create view view_name as select 常量;
例子:create view view_test1 as select 3.1415926;
查询:select * from view_test1;
(2).聚合函数(SUM,MIN.,MAX,COUNT等)查询语句视图:
create view view_name as select 函数(属性名) from table_name;
例子:create view view test2 as select count(name) from t_student;
(3).排序功能的视图:
create view view_name as select 属性名 from table_name order by 属性名 顺序;
其中顺序分为DESC 和 ASC ,前者降序,后者升序.
(4).表内连接查询语句:
create view view_name as select 属性 from table1_name,table2_name where 条件;
例子:create view view_testt4 as select s.name from t_student as s,t_group as g where s.group_id = g.id and g.id = 2;其中的table_name 后的as的意思是起别名;
(5).表外连接(LEFT JOIN和RIGHT JOIN)查询语句:
create view view_name as select 属性名 from table1_name LEFT JOIN table2_name on 条件 where 条件;
左连接A,B表结果为A的全部记录和符合条件的B的记录
例子:create view view_test5 as select s.name from t_student as s LEFT JOIN t_group as g on s.group_id = g.id where g.id = 2;
(6).子查询相关查询语句:
create view view_name as select 属性名 from table1_name where 属性名 in (select 属性名 from table2_name);
例子:create vieww view_test6 as select s.name from t_student as s where s.group_id in (select id from t_group);
(7).记录联合(UNION和UNION ALL):
create view view_name as 查询语句1 UNION ALL 查询语句2;
查询的内容应该相同.
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