テーブル内の直前のエントリを取得しようとしています

Question

特定のイベントを過ぎたテーブルの最新のエントリを取得しようとしています。この主なテーブルには、ユーザーのID、発生したイベントの種類、タイムスタンプが含まれています。

これはどこ私は現在でいますされています（個々のイベントのためのdupesは、私が想定していないが）

SELECT cc.RefNo 
    ,cc.Subcase 
    ,ev.EventDate 
    ,evt.EventCode 
    ,ev.Amount 
    ,previousevent.EventCode as [previous Event] 
    ,previousevent.previousdate as [date previous event] 
    FROM event ev JOIN EventTemplate evt ON ev.EventTemplateID = evt.ID 
    JOIN CCase cc ON cc.ID = ev.CCaseID 
    JOIN (SELECT MAX(ev.EventDate) as previousdate, evt.EventCode, CCaseID 
          FROM Event ev JOIN EventTemplate evt ON ev.EventTemplateID = evt.ID 
          WHERE (evt.EventCode LIKE 'SI%' OR evt.EventCode LIKE 'SM%') 
          Group by CCaseID, evt.EventCode) as previousevent 
    ON previousevent.CCaseID = cc.ID 
    AND previousevent.previousdate < ev.EventDate 

このため、出力は私の以前のすべてのイベントを与えています。私は今、RefNo、Subcase、EventDate、EventCodeの組み合わせごとに最新のものに到達する方法を探しています。

Answer 1

テストされていないが、おそらくRow_Number()と協力しWITH TIES句はここ

SELECT Top 1 with ties 
     cc.RefNo 
     ,cc.Subcase 
     ,ev.EventDate 
     ,evt.EventCode 
     ,ev.Amount 
     ,previousevent.EventCode as [previous Event] 
     ,previousevent.previousdate as [date previous event] 
    FROM event ev JOIN EventTemplate evt ON ev.EventTemplateID = evt.ID 
    JOIN CCase cc ON cc.ID = ev.CCaseID 
    JOIN (SELECT MAX(ev.EventDate) as previousdate, evt.EventCode, CCaseID 
          FROM Event ev JOIN EventTemplate evt ON ev.EventTemplateID = evt.ID 
          WHERE (evt.EventCode LIKE 'SI%' OR evt.EventCode LIKE 'SM%') 
          Group by CCaseID, evt.EventCode) as previousevent 
    ON previousevent.CCaseID = cc.ID 
    AND previousevent.previousdate < ev.EventDate 
    Order By Row_Number() over (Partition By RefNo, Subcase, EventCode Order By EventDate Desc) 

Answer 2

役立つ可能性がおそらくそれを行うための最も簡単な方法は、CTEとROW_NUMBERである：ここでは

;WITH CTE AS 
(
    SELECT cc.RefNo 
     ,cc.Subcase 
     ,ev.EventDate 
     ,evt.EventCode 
     ,ev.Amount 
     ,previousevent.EventCode as [previous Event] 
     ,previousevent.previousdate as [date previous event] 
     , ROW_NUMBER() OVER (PARTITION BY cc.RefNo ,cc.Subcase ,ev.EventDate, evt.EventCode ORDER BY previousevent.previousdate DESC) AS rn 
     FROM event ev JOIN EventTemplate evt ON ev.EventTemplateID = evt.ID 
     JOIN CCase cc ON cc.ID = ev.CCaseID 
     JOIN (SELECT MAX(ev.EventDate) as previousdate, evt.EventCode, CCaseID 
           FROM Event ev JOIN EventTemplate evt ON ev.EventTemplateID = evt.ID 
           WHERE (evt.EventCode LIKE 'SI%' OR evt.EventCode LIKE 'SM%') 
           Group by CCaseID, evt.EventCode) as previousevent 
     ON previousevent.CCaseID = cc.ID 
     AND previousevent.previousdate < ev.EventDate 
) 

SELECT cc.RefNo 
     ,cc.Subcase 
     ,ev.EventDate 
     ,evt.EventCode 
     ,ev.Amount 
     ,previousevent.EventCode as [previous Event] 
     ,previousevent.previousdate as [date previous event] 
FROM CTE 
WHERE rn = 1