[sql]视图

视图

视图是一张虚拟的表,本质是一坨sql语句(可能是连表查询等非常复杂的一段sql)

- 模拟视图
select nid from partment where nid > 2; # 将它的结果作为下面一句的条件

select * from (select nid from partment where nid > 2) as A;

创建视图

create view v1 as
	select man.name as mname,woman.name as wname from relationship
	LEFT JOIN man on relationship.man_nid = man.nid
	LEFT JOIN woman on relationship.woman_nid = woman.nid
	where man.name = 'aaron'

查看视图(即一张表),会随着依赖的表动态更新的.

修改视图

alter view v1 as
select * from man where nid >= 1;

在查看视图,已动态更新了.

删除视图

drop view v1;