如何寫一個SQL查詢下面的情形

Question

銷售

order id : 1(primary key) 
Billing address id -250 
Shipping address id -285 

地址表中包含了以下條目

id :250 
Addressline1 : XXX 
Addressline2 :YYY 

id :285 
Addressline1 : AAA 
Addressline2 :BBB 

如何編寫一個查詢來檢索單個查詢order id, billing address, shipping address？

Answer 1

你可以加入到address表多次（這裏採用的outer join - 取決於潛在null值）：

select s.id, 
    billing.Addressline1, 
    shipping.Addressline1 
from sales s 
    left join address billing on s.billingaddressid = billing.id 
    left join address shipping on s.shippingaddressid = shipping.id 

• A Visual Explanation of SQL Joins

Answer 2

使用與加入下面的查詢。以下是示例代碼。

select order.orderid, 
     ad1.Addressline1, 
     ad1.Addressline2, 
     ad2.Addressline1, 
     ad2.Addresslinne2 
from order 
join address ad1 on ad1.id=order.billingaddressid 
join address ad2 on ad2.id=order.shippingaddressid