集合函數sum沒有工作確定子查詢

Question

時，這是我的查詢：

SELECT 
    Sum(IsNull(CircuitCourtFeeCap, 0) + IsNull(CircuitCourtCourtTime, 0) + IsNull(CircuitCourtWaiverFee, 0) + IsNull(CircuitCourtExpenseFee, 0)) AS TotalApproved, 
    Sum(IsNull(e.FeeAmountCap, 0)) AS TotalFeeCap, 
    Sum(IsNull((
       SELECT Claimed 
       FROM [dbo].[CourtTimes] ct 
       WHERE ct.DocumentNameID = dn.DocumentNameID 
       ), 0)) AS TotalCourtTime 
FROM DocumentNames dn 
LEFT JOIN Expenses e ON dn.DocumentNameID = e.DocumentNameID 

這是超級簡單。除了這片線的各種形式的金額不工作：

Sum(IsNull((Select Claimed From [dbo].[CourtTimes] ct Where ct.DocumentNameID = dn.DocumentNameID), 0)) As TotalCourtTime 

我得到這個錯誤：Cannot perform an aggregate function on an expression containing an aggregate or a subquery.

任何想法如何解決這個問題呢？

Answer 1

就像錯誤說的那樣，你不能執行一個聚合函數（sum()在本例子查詢中）。相反，加入其他表中您FROM條款：

SELECT 
    Sum(IsNull(CircuitCourtFeeCap, 0) + IsNull(CircuitCourtCourtTime, 0) + IsNull(CircuitCourtWaiverFee, 0) + IsNull(CircuitCourtExpenseFee, 0)) AS TotalApproved, 
    Sum(IsNull(e.FeeAmountCap, 0)) AS TotalFeeCap, 
    Sum(IsNull(ct.CourtTime, 0)) AS TotalCourtTime 
FROM DocumentNames dn 
    LEFT OUTER JOIN (SELECT DocumentNameID, sum(claimed) as CourtTime FROM [dbo].[CourtTimes] GROUP BY DocumentNameID) ct 
     ON ct.DocumentNameID = dn.DocumentNameID 
    LEFT OUTER JOIN Expenses e 
     ON dn.DocumentNameID = e.DocumentNameID; 

更新這個答案移動[CourtTimes]表連接成一個子查詢，以便它可以在DocumentNameID級預聚合加入之前。