SQL服務器條件連接

Question

我必須根據可以爲空的值來選擇連接列來連接。 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爲null，則我不得不使用shoporders.DeliveryAddressId

任何線索？

在此先感謝

Answer 1

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

Answer 2

你可以嘗試

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：對於聚結的定義，見MSDN。總結如下

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

CASE 

    WHEN (expression1 IS NOT NULL) THEN expression1 

    WHEN (expression2 IS NOT NULL) THEN expression2 

    ... 

    ELSE expressionN 

END 

Answer 3

您可以嘗試

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