視圖的創(chuàng)建

• 視圖用create view語句來創(chuàng)建
• 使用show create view viewname來查看創(chuàng)建視圖的語句
• 用drop view viewname刪除視圖
• 更新視圖是，可以先用drop再用create，也可以直接用create or replace view

利用視圖簡(jiǎn)化復(fù)雜的聯(lián)結(jié)

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';

使用視圖重新格式化檢索出來的數(shù)據(jù)

\1.PNG

\2.PNG

使用視圖過濾不想要的數(shù)據(jù)

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

使用視圖與計(jì)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;

參考書籍：

• MySQL必知必會(huì)