SQL查詢計算列

Question

請幫我查詢。假設我們有列的表格：

• 交易
• 開始時間
• 結束時間

現在，我需要的計算列（值=結束時間 - STARTIME）查詢。 其實我需要將用戶分組（交易有用戶的FK），並按平均花費時間進行排序。

Answer 1

你應該看看DateDiff函數。沒有指定的時間跨度的單位，所以我認爲在我的解決方案秒：

Select ... 
From dbo.Users As U 
    Join (
      Select T.UserId, Avg(DateDiff(s, T.StartTime, T.EndTime)) As AvgTimespan 
      From dbo.Transactions As T 
      Group By T.UserId 
      ) As Z 
     On Z.UserId = U.Id 
Order By Z.Timespan Desc 

Answer 2

SELECT u.userid 
     ,AVG(DATEDIFF(second, StartTime, EndTime) AS AvgTime 
FROM trxn AS t 
INNER JOIN users AS u 
    ON trxn.userid = u.userid 
GROUP BY u.userid 
ORDER BY AVG(DATEDIFF(second, StartTime, EndTime)