MySql 视图

视图的创建

• 视图用create view语句来创建
• 使用show create view viewname来查看创建视图的语句
• 用drop view viewname删除视图
• 更新视图是，可以先用drop再用create，也可以直接用create or replace view

利用视图简化复杂的联结

create view productcustomers as 
select cust_name, cust_contact, prod_id
from customers, orders, orderitems
where customers.cust_id = orders.cust_id
and orderitems.order_num = orders.order_num;

//使用
select cust_name, cust_contact 
from productcustomers
where prod_id = 'TNT2';

使用视图重新格式化检索出来的数据

\1.PNG \2.PNG

使用视图过滤不想要的数据

create view customeremaillist as
select cust_id, cust_name, cust_email
from cutomers
where cust_email is not null;

使用视图与计算字段

create view orderitemsexpanded as
select order_num,
     prod_id,
     quantity,
     item_price,
     quantity*item_price as expanded_price
from orderitems;

//使用
select * from orderitemsexpanded
where order_num = 20005;

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参考书籍：

• MySQL必知必会