SQL服務器條件連接

Question

我必須根據一個可以為null的值來選擇相關列。 詳細：

SELECT shoporders.orderid, 
   shopaddresses.companyname, 
   shopaddresses.firstname, 
   shopaddresses.lastname, 
   shopaddresses.address1,  
FROM   shoporders 
   INNER JOIN shopaddresses 
           ON shoporders.InvoiceAddressId = shopaddresses.addressid
where orderid = 110
order by shoporders.createddate desc

如果shoporders.InvoiceAddressId為null，那么我必須使用shoporders.DeliveryAddressId

任何線索？

提前致謝

Answer 1

ON coalesce(shoporders.InvoiceAddressId, shoporders.DeliveryAddressId) = shopaddresses.addressid

Answer 2

你可以試試

SELECT shoporders.orderid, 
   shopaddresses.companyname, 
   shopaddresses.firstname, 
   shopaddresses.lastname, 
   shopaddresses.address1,  
FROM   shoporders 
   INNER JOIN shopaddresses 
           ON COALESCE (shoporders.InvoiceAddressId, shoporders.DeliveryAddressId)  = shopaddresses.addressid
where orderid = 110
order by shoporders.createddate desc

編輯：有關合並的定義，請參閱MSDN 。 以下摘要

返回其參數中的第一個非空表達式。 COALESCE(expression1,...n)等效於以下CASE表達式：

CASE

   WHEN (expression1 IS NOT NULL) THEN expression1

   WHEN (expression2 IS NOT NULL) THEN expression2

   ...

   ELSE expressionN

END

Answer 3

你可以試試

 SELECT shoporders.orderid, 
       shopaddresses.companyname, 
       shopaddresses.firstname, 
       shopaddresses.lastname, 
       shopaddresses.address1,  
       FROM   shoporders 
       INNER JOIN shopaddresses 
       ON( 
          (shoporders.InvoiceAddressId IS NOT NULL  
                  AND shoporders.InvoiceAddressId = shopaddresses.addressid)
          OR (shoporders.DeliveryAddressId = shopaddresses.addressid) 
          )

       WHERE orderid = 110
       ORDER BY shoporders.createddate DESC