SQL服务器条件连接

Question

I have to choose the according column to join basing on a value that can be null. In detail:

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

if shoporders.InvoiceAddressId is null then I have to use shoporders.DeliveryAddressId

Any clue?

Thanks in advance

Answer 1

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

Answer 2

you could try

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

Edit: For a definition of coalesce see MSDN . A Summary below

Returns the first nonnull expression among its arguments. COALESCE(expression1,...n) is equivalent to the following CASE expression:

CASE

   WHEN (expression1 IS NOT NULL) THEN expression1

   WHEN (expression2 IS NOT NULL) THEN expression2

   ...

   ELSE expressionN

END

Answer 3

You can try

 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