07-PGView

PGView

将一些复杂的查询操作封装起来，同时隐藏敏感的信息。但是不推荐视图进行写操作。

简而言之，视图就是一些sql语句。

Syntax:
CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] [ RECURSIVE ] VIEW name [ ( column_name [, ...] ) ]
    [ WITH ( view_option_name [= view_option_value] [, ... ] ) ]
    AS query
    [ WITH [ CASCADED | LOCAL ] CHECK OPTION ]

构建简单的视图

postgres=# create view vw_score as (select student_id from student);

CREATE VIEW

使用视图

postgres=# select * from vw_score;
 student_id 
------------
          2
          3
(2 rows)

对于单表简单视图可以修改，同时修改的就是原表。但如果是多表联查，就不可修改。

update vw_score set id = 5 where student_id = 2;

update vw_student_score set id = 5 where student_id = 2;
ERROR:错误:无法更新视图"ww student score"
DETAIL: 不来自单表或单视图的视图不能自动更新...