SQL練習 某書第八章（改變資料

1.基於聯結的delete

注意1：

注意2：基於聯結的update

3.通過表表示式修改資料

3-1：如何使用

--必須使用：視窗函式

練習： 

1.#8.1-2 從sales.customers表插入所有具有訂單的客戶到dbo.customers'

-- 注意有訂單要求 sales.customers的custid存在於sales.orders的custid

insert into dbo.customers(custid,companyname,country,region,city)

select custid,companyname,country,region,city
from sales.customers as sc
where exists
(select * from sales.orders as so
where so.custid = sc.custid);

#8.3 刪除dbo.orders的名稱為巴西的訂單行，

-- 而且dbo.orders沒有名字 需要從 dbo.customers查詢名字  

delete from dbo.orders 

where exists
(select * from dbo.customers as dc
where orders.custid = do.custid
and dc.country = 'brazil');
-- 做法2：
delete from o
from dbo.orders as o
join dbo.customers as c
on o.custid = c.custid
where country = 'brazil'