獲取另一列不等於零的列的最大日期

Question

我正在嘗試獲取用戶提供活動作爲查詢一部分的最近活動日期。下面是該查詢：

USE SCRUMAPI2 

DECLARE @userParam VARCHAR(100) 
    ,@statusParam VARCHAR(100) 

SET @userParam = '%' 
SET @statusParam = '%' 

SELECT ROW_NUMBER() OVER (
     ORDER BY TSK.[Status] DESC 
     ) AS 'RowNumber' 
    ,PDT.[Name] AS Project 
    ,(
     CASE WHEN (
        STY.KanBanProductId IS NOT NULL 
        AND STY.SprintId IS NULL 
        ) THEN 'KanBan' WHEN (
        STY.KanBanProductId IS NULL 
        AND STY.SprintId IS NOT NULL 
        ) THEN 'Sprint' END 
     ) AS ProjectType 
    ,STY.[Number] StoryNumber 
    ,STY.Title AS StoryTitle 
    ,TSK.[Name] AS Task 
    ,CONVERT(VARCHAR(20), STY.Effort) AS Effort 
    ,CONVERT(VARCHAR(20), TSK.OriginalEstimateHours) AS OriginalEstimateHours 
    ,ISNULL(SUM(DTH.[Hours]), 0) AS [TotalHours] 
    ,TSK.[Status] AS [Status] 
FROM Task TSK 
LEFT JOIN DailyTaskHours DTH ON TSK.PK_Task = DTH.TaskId 
LEFT JOIN Story STY ON TSK.StoryId = STY.PK_Story 
LEFT JOIN Sprint SPT ON STY.SprintId = SPT.PK_Sprint 
LEFT JOIN Product PDT ON STY.ProductId = PDT.PK_Product 
WHERE TSK.PointPerson LIKE @userParam 
    AND TSK.[Status] LIKE @statusParam 
GROUP BY LEN(STY.[Number]) 
    ,STY.[Number] 
    ,TSK.[Status] 
    ,STY.Title 
    ,PDT.[Name] 
    ,TSK.CreateDate 
    ,TSK.[Name] 
    ,STY.KanBanProductId 
    ,STY.SprintId 
    ,TSK.OriginalEstimateHours 
    ,STY.Effort 
ORDER BY CASE TSK.[Status] WHEN 'Not Started' THEN 1 WHEN 'In Progress' THEN 2 WHEN 'Impeded' THEN 3 WHEN 'Done' THEN 4 END 

我想用的功能添加行，像這樣：

,MAX(DTH.ActivityDate WHERE DTH.Hours != 0) AS LatestActivityDate 

然而，這將導致一個語法錯誤。我無法將DTH.Hours！= 0添加到WHERE語句中，因爲我不想讓整個查詢過濾掉它。那麼如何獲得最新的ActivityDate，其中小時數不等於零？

這裏是什麼DTH表看起來像以供參考：

Answer 1

一個CASE expression是我們的朋友：

MAX(CASE WHEN DTH.Hours != 0 THEN DTH.ActivityDate END) AS LatestActivityDate