分層數據所需的cte實現

Question

僅爲SQL Server 2008尋求優化代碼（因爲Lag和Lead函數在SQL Server 2008中不可用）。對於以下要求（最後一個記錄結束日期爲空或不爲空）

業務規則是：

結束日期應該開始日期爲下一條規則，否則規則不應該被認爲是連續的，將被視爲一個其他規則系列，如下例所示，由於第四條記錄和第七條記錄規則已被制動，所以有三個系列。

RuleId Name StartDate   EndDate 
-----------------------------------------------------------  
2  TP1  1/1/2015 00.00.00 1/31/2015 00.00.00 
2  TP1  1/31/2015 00.00.00 2/28/2015 00.00.00 
2  TP1  2/28/2015 00.00.00 3/15/2015 00.00.00 
2  TP1  3/18/2015 00.00.00 11/28/2015 00.00.00 
2  TP1  11/28/2015 00.00.00 4/30/2016 00.00.00 
2  TP1  4/30/2016 00.00.00 10/5/2016 00.00.00 
2  TP1  10/25/2016 00.00.00 11/15/2016 00.00.00 
2  TP1  11/15/2016 00.00.00 Null 

結果應該是以下

2  TP1  1/1/2015 00.00.00 3/15/2015 00.00.00 
2  TP1  3/18/2015 00.00.00 10/5/2016 00.00.00 
2  TP1  10/25/2016 00.00.00 Null 

Answer 1

您可以在此基礎上你可以將你的結果做PARTITION BY一個ROW_NUMBER()，然後做一個自我與RN = RN + 1加入，做一個DATEDIFF。

嘗試是這樣的

DECLARE @Rules TABLE(RuleId INT,Name CHAR(3), StartDate DATE,   EndDate DATE) 

INSERT INTO @Rules VALUES 
(3 ,'TP3', '3/18/2015', '11/28/2015'), 
(3 ,'TP3', '11/28/2015', '4/30/2016'), 
(3 ,'TP3', '4/30/2016', '10/5/2016'), 
(3 ,'TP3', '10/25/2016', '11/15/2016'), 
(3 ,'TP3', '11/15/2016', null) 


;WITH CTE AS 
(
SELECT ROW_NUMBER() OVER(PARTITION BY RuleID ORDER BY StartDate) rn,* 
FROM @Rules 
), CTE2 AS 
(
SELECT ISNULL(DATEDIFF(day,C1.EndDate,C2.StartDate),0) diff,C1.* 
FROM CTE C1 
LEFT JOIN CTE C2 ON C1.rn + 1 = C2.rn 
AND C1.RuleId = C2.RuleId 
) 
SELECT RuleId,Name,MIN(StartDate) StartDate,NULLIF(MAX(CASE WHEN EndDate IS NULL THEN '2999/12/31' ELSE EndDate END),'2999/12/31') EndDate 
FROM 
(
SELECT C2.Diff,C1.RuleId,C1.Name,C1.StartDate,C1.EndDate 
FROM CTE2 C1 
CROSS APPLY (SELECT ISNULL(SUM(Diff),0) Diff FROM CTE2 C2 WHERE C1.StartDate > C2.StartDate AND C1.RuleId = C2.RuleId) C2 
) C 
GROUP BY RuleId,Name,Diff 
ORDER BY RuleId,Diff