pl/sql编程（四）

1.单表视图

create view goods_view 
as 
select goodsid,goodsname remark from goods where remark is not null
       
select * from goods_view

2.多表视图

create view goods_sa_view 
as 
select sa.said,g.goodsid,g.goodsname,sa.sa_quantity,g.remark from goods g join sa on g.goodsid = sa.goodsid

select * from goods_sa_view

3.视图的视图

create view goods_view_view 
as 
select remark,count(*) num from goods_view group by remark

select * from goods_view_view

4.无源表视图
　也可以被称为强制创建视图，该视图虽然被创建了，但还不能使用，等到源表创建完成后，就可以正常使用了

create force view notable_view
as 
select * from tb_not_exsit

5.设置视图只读

create view goods_view_ron
as 
select * from goods
with read only

6.设置视图的检查约束

　对于不符合视图的约束条件的修改和增加进行限制

create view goods_view_check
as 
select * from goods where remark is not null
with check option

7.查看视图

select view_name,text from user_views

8.修改视图

create or replace view goods_view
as 
select goodsid,goodsname, remark from goods where remark is not null

9.删除视图

drop view notable_view