MAX多列的日期？

你怎麼每行返回的多個列的最大數值1：MAX多列的日期？

表名[RefNumber，FirstVisitedDate，SecondVisitedDate，RecoveryDate，ActionDate]

我想要的MAXDATE（FirstVisitedDate，SecondVisitedDate，RecoveryDate，ActionDate）這些日期爲單列中的所有行，並且我希望另一個新列（Acion）依賴於Max日期列，例如：如果Max日期來自FirstVisitedDate，那麼它將是'FirstVisited'，或者如果Max日期來自SecondVisitedDate，那麼它將是' SecondVisited'...

總結果喜歡：

選擇RefNumber，MAXDATE，行動從表組由RefNumber

來源

2014-06-04 user3583912

我寫了一個自定義函數來做到這一點：

CREATE FUNCTION [dbo].[MaxOf5] 
(
    @D1 DateTime, 
    @D2 DateTime, 
    @D3 DateTime, 
    @D4 DateTime, 
    @D5 DateTime 
) 
RETURNS DateTime 
AS 
BEGIN 
    DECLARE @Result DateTime 

    SET @Result = COALESCE(@D1, @D2, @D3, @D4, @D5) 

    IF @D2 IS NOT NULL AND @D2 > @Result SET @Result = @D2 
    IF @D3 IS NOT NULL AND @D3 > @Result SET @Result = @D3 
    IF @D4 IS NOT NULL AND @D4 > @Result SET @Result = @D4 
    IF @D5 IS NOT NULL AND @D5 > @Result SET @Result = @D5 

    RETURN @Result 
END

要調用該方法，並計算出你的Action列，這應該工作：

SELECT 
    MaxDate, 
    CASE WHEN MaxDate = FirstVisitedDate THEN 'FirstVisited' 
     WHEN MaxDate = SecondVisitedDate THEN 'SecondVisited' 
     WHEN MaxDate = RecoveryDate THEN 'Recovery' 
     WHEN MaxDate = ActionDate THEN 'Action' 
    END AS [Action] 
FROM (
    SELECT 
     RefNumber, 
     dbo.MaxOf5(FirstVisitedDate, SecondVisitedDate, RecoveryDate, ActionDate) AS MaxDate, 
     FirstVisitedDate, SecondVisitedDate, RecoveryDate, ActionDate 
    FROM table 
) AS data

請注意，您可以將多個日期綁定到最大日期。在這種情況下，您的WHEN子句的順序決定哪一個獲勝。

來源

2014-06-04 23:19:27 David

嗨大衛，感謝您的回覆..一切正常與您的代碼，但我不能做GROUP BY RefNumber ..可以請檢查一次..謝謝 – user3583912

@ user3583912，如果有2行具有相同的'RefNumber'，你如何選擇要返回的日期和操作？ – David

;WITH cte AS (
    -- Build table of date 
    SELECT [RefNumber], 
     [ActionDate]= [FirstVisitedDate], 
     [Action] = 'First Visited' 
    FROM [Table1] 
    UNION ALL 
    SELECT [RefNumber], 
     [SecondVisitedDate], 
     'Second Visited' 
    FROM [Table1] 
    UNION ALL 
    SELECT [RefNumber], 
     [RecoveryDate], 
     'Recover' 
    FROM [Table1] 
), cte2 AS (
    -- Add row_number to pull most recent to top 
    SELECT [RefNumber], 
      [Action], 
      [ActionDate], 
      [DateRank] = 
       ROW_NUMBER() OVER (PARTITION BY RefNumber 
           ORDER BY [ActionDate] DESC) 
    FROM [cte] 
) 
-- select only the most recent 
SELECT * 
FROM cte2 
WHERE [DateRank] = 1

來源

2014-06-04 23:21:12 Malk

蠻力的方法是不是四列如此糟糕：

select (case when FirstVisitedDate >= SecondVisitedDate and 
        FirstVisitedDate >= RecoveryDate and 
        FirstVisitedDate >= ActionDate 
      then FirstVisitedDate 
      when SecondVisitedDate >= RecoveryDate and 
        SecondVisitedDate >= ActionDate 
      then SecondVisitedDate 
      when RecoveryDate >= ActionDate 
      then RecoveryDate 
      else ActionDate 
     end), 
     (case when FirstVisitedDate >= SecondVisitedDate and 
        FirstVisitedDate >= RecoveryDate and 
        FirstVisitedDate >= ActionDate 
      then 'FirstVisitedDate' 
      when SecondVisitedDate >= RecoveryDate and 
        SecondVisitedDate >= ActionDate 
      then 'SecondVisitedDate' 
      when RecoveryDate >= ActionDate 
      then 'RecoveryDate' 
      else 'ActionDate' 
     end)  
from table t;

編輯：

在group by這樣做僅僅是一個增加的聚合函數問題：

select RefNumber, 
     (case when max(FirstVisitedDate) >= max(SecondVisitedDate) and 
        max(FirstVisitedDate) >= max(RecoveryDate) and 
        max(FirstVisitedDate) >= max(ActionDate) 
      then max(FirstVisitedDate 
      when max(SecondVisitedDate) >= max(RecoveryDate) and 
        max(SecondVisitedDate) >= max(ActionDate) 
      then max(SecondVisitedDate) 
      when max(RecoveryDate) >= max(ActionDate) 
      then max(RecoveryDate) 
      else max(ActionDate) 
     end), 
     (case when max(FirstVisitedDate) >= max(SecondVisitedDate) and 
        max(FirstVisitedDate) >= max(RecoveryDate) and 
        max(FirstVisitedDate) >= max(ActionDate) 
      then 'FirstVisitedDate' 
      when max(SecondVisitedDate) >= max(RecoveryDate) and 
        max(SecondVisitedDate) >= max(ActionDate) 
      then 'SecondVisitedDate' 
      when max(RecoveryDate) >= max(ActionDate) 
      then 'RecoveryDate' 
      else 'ActionDate' 
     end)  
from table t 
group by RefNumber;

來源

2014-06-04 23:24:00

嗨戈登Linoff，感謝您的答覆。但我有9個日期列Maxdate ..以上只是爲了示例..謝謝 – user3583912

@ user3583912。。。邏輯對於九列來說並不難，只是很多複製和粘貼。但它確實強調了其他數據庫中「最大（）」和「最少（）」函數的有用性。 –

我會這樣做..你的權利是那些在Mysql中有用的功能 – user3583912

SELECT RecordID, MaxDate 
FROM SourceTable 
    CROSS APPLY (SELECT MAX(d) MaxDate 
       FROM (VALUES (date1), (date2), (date3), 
          (date4), (date5), (date6), 
          (date7)) AS dates(d)) md

來源

2014-06-05 11:37:23 EarlOfEnnui

MAX多列的日期？

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