SQL创建视图的注意事项及说明

CREATE VIEW <视图名称>(<列名1>,<列名2>,...) AS 
<SELECT语句>
from  表名
group by 列名；-- 该语句可以选择或者不写该语句，两者的区别就是是否有汇总

drop view profit;
create view profit (种类,售价, 进价,利润)
As 
select product_type,sale_price,purchase_price,sale_price - purchase_price as profit
from product
group by product_type;

select * from profit;

drop view profit1;
create view profit1 (种类,售价, 进价,利润)
As 
select product_type,sale_price,purchase_price,sale_price - purchase_price as profit
from product; 
select * from profit1;

ALTER VIEW <视图名> AS <SELECT语句>
-- 例如：
ALTER VIEW profit
    AS
        SELECT product_type, sale_price
          FROM Product
         WHERE reGISt_date > '2009-09-11';

select a.name as username, b.name as goodsname from user as a, goods as b, ug as c where a.id=c.userid and c.goodsid=b.id;

create view other as select a.name as username, b.name as goodsname from user as a, goods as b, ug as c where a.id=c.userid and c.goodsid=b.id;

select * from other;

create view user as select a.name,a.age,b.sex from usera as a, userb as b where a.name=b.name;

create view other as select a.name, a.age from user as a;