Question

我的查询包含太多的select语句。因此我使用了条件聚合。该查询引用SQL Server 2008中 Instock 表中的数据，最终查询如下所示：

select 
    SUM(CASE WHEN MONTH = '2013-8-1' THEN CurrentStock ELSE 0 END) as CurrentStock,
    Isnull(Sum(CASE WHEN MONTH = '2014-2-1' THEN CPU ELSE 0 END), 0) - Isnull(Sum(CASE WHEN MONTH = '2013-8-1' THEN CPU ELSE 0 END), 0) as CPU,
    SUM(CASE WHEN Month = '2013-8-1' THEN NonCPUWIP ELSE 0 END) as NonCPU,
    Isnull(Sum(CASE WHEN MONTH = '2014-2-1' THEN ScrapDiscarded ELSE 0 END), 0) - Isnull(Sum(CASE WHEN MONTH = '2013-8-1' THEN ScrapDiscarded ELSE 0 END), 0) as Scrap,
    SUM(CASE WHEN Month = '2013-8-1' THEN WaitingForApproval ELSE 0 END) as WFA  
from 
    Instock
where 
    Vendor = 'abc'

问题是需要包含的最后一个查询。它从OutStock表中获取数据，但我希望在上面的表中包含该查询，以便将结果作为单行返回。我能够使用嵌套查询来满足要求，但我希望使用条件聚合获得相同的结果，以保证数据库性能的平滑性。

需要包含的查询是：

select 
    COUNT(Product) as Despatched 
from 
    OutStock 
where 
    DispatchDate between '2013-8-1' and '2014-2-1' 
    and Vendor = 'abc'`

因此，我希望将两者结合起来作为单个查询执行，这将返回单行

Answer 1

只需在第一个查询的列列表中添加第二个查询，因为它只返回一行。试试这个。

SELECT Sum(CASE
             WHEN MONTH = '2013-8-1' THEN CurrentStock
             ELSE 0
           END)                                 AS CurrentStock,
       Isnull(Sum(CASE WHEN MONTH = '2014-2-1' THEN CPU ELSE 0 END), 0) - 
       Isnull(Sum(CASE WHEN MONTH = '2013-8-1' THEN CPU ELSE 0 END), 0) AS CPU,
       Sum(CASE WHEN Month = '2013-8-1' THEN NonCPUWIP ELSE 0 END) AS NonCPU,
       Isnull(Sum(CASE WHEN MONTH = '2014-2-1' THEN ScrapDiscarded ELSE 0 END), 0) - 
       Isnull(Sum(CASE WHEN MONTH = '2013-8-1' THEN ScrapDiscarded ELSE 0 END), 0)AS Scrap,
       Sum(CASE WHEN Month = '2013-8-1' THEN WaitingForApproval ELSE 0 END) AS WFA,
       (SELECT Count(STBSerialNUMBER)
        FROM   OutStock
        WHERE  DispatchDate BETWEEN '2013-8-1' AND '2014-2-1'
                AND Vendor = 'abc' ) as Despatched
FROM   Instock I
WHERE  Vendor = 'abc'

更新：

如果您想要每个模型的结果计数，请将subquery转换为correlated subquery。应该像

  (SELECT Count(STBSerialNUMBER)
   FROM   OutStock O
   WHERE o.model = i.model  -- here is the change
   AND O.DispatchDate BETWEEN '2013-8-1' AND '2014-2-1'
   AND o.Vendor = 'abc')

对于model表格中的每个Instock，count中的outstock将被计算在内。

或者您也可以使用Left Join。首先使用模型计算model表Outstock中每个join的计数结果返回Instock表

   ....
   From Instock I Left Join 
   (SELECT Count(STBSerialNUMBER) OutStock_count,Model
   FROM   OutStock O
   WHERE  O.DispatchDate BETWEEN '2013-8-1' AND '2014-2-1'
   AND o.Vendor = 'abc'
   Group by Model) O on o.model = i.model

在SQL Server 2008中使用条件聚合

1 个答案: