如何在SQL GROUP BY子句中返回空组

2019年7月29日 234次阅读

我有一个查询来返回在每个位置花费了多少合同和合同,返回的内容如下：

Location     | ContractStatus | Expenses
-------------+----------------+---------
New York     | Ad-hoc         | 2043.47
New York     | Contracted     | 2894.57
Philadelphia | Ad-hoc         | 3922.53
Seattle      | Contracted     | 2522.00

问题是,对于所有临时或所有合同费用的地点,我只获得一行.我想为每个位置返回两行,如下所示：

Location     | ContractStatus | Expenses
-------------+----------------+---------
New York     | Ad-hoc         | 2043.47
New York     | Contracted     | 2894.57
Philadelphia | Ad-hoc         | 3922.53
Philadelphia | Contracted     |    0.00
Seattle      | Ad-hoc         |    0.00
Seattle      | Contracted     | 2522.00

有什么方法可以通过SQL实现这一点吗？这是我正在使用的实际查询(SQL Server 2005)：

SELECT Location, 
     CASE WHEN Orders.Contract_ID IS NULL 
          THEN 'Ad-hoc' ELSE 'Contracted' END 
                     AS ContractStatus,
     SUM(OrderTotal) AS Expenses
FROM Orders
GROUP BY Location, 
    CASE WHEN Orders.Contract_ID IS NULL 
         THEN 'Ad-hoc' ELSE 'Contracted' END
ORDER BY Location ASC, ContractStatus ASC

最佳答案 是的,构造一个表达式,仅返回adhoc的ordertotal,其他的返回0,另一个执行相反的操作,并对这些表达式求和.这将包括每个位置一行,其中两列用于adhoc,一列用于Contracted …

 SELECT Location,  
     Sum(Case When Contract_ID Is Null Then OrderTotal Else 0 End) AdHoc,
     Sum(Case When Contract_ID Is Null Then 0 Else OrderTotal  End) Contracted
 FROM Orders 
 GROUP BY Location

如果你真的想要每个单独的行,那么一种方法是：

 SELECT Location, Min('AdHoc') ContractStatus,
     Sum(Case When Contract_ID Is Null 
              Then OrderTotal Else 0 End) OrderTotal
 FROM Orders 
 GROUP BY Location
 Union
 SELECT Location, Min('Contracted') ContractStatus,
     Sum(Case When Contract_ID Is Null 
              Then 0 Else OrderTotal  End) OrderTotal
 FROM Orders 
 GROUP BY Location
 Order By Location
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