SQL Server 2012+：按时间段合并元素

我已经为这个问题挣扎了一段时间，我需要一些帮助。 我有以下疑问：

CREATE TABLE Example(
Start NVARCHAR(8),
Endd NVARCHAR(8),
Col1 NVARCHAR(2),
Col2 NVARCHAR(2));

INSERT into Example (Start,Endd,Col1,Col2)
VALUES ('20130801','20140316','02','01'),
('20140317','20140319','04','02'),
('20140320','20140320','04','02'),
('20140321','20140421','02','Z8'),
('20140422','20140429','02','Z9'),
('20140430','20140902','04','02'),
('20140903','20150201','04','02'),
('20150202','20150223','04','02'),
('20150224','20150527','04','02'),
('20150528','99991231','04','02')
;

select MIN(Start)AS Start,MAX(Endd) AS Endd,Col1,Col2 from 
(
    SELECT top (100000000) Start, Endd,Col1, Col2,dense_rank() over(partition by Col1, Col2 order by Start,Endd) as rank 
    ,LEAD (Col1) OVER (order by Start,Endd DESC) as l1
    ,LEAD (Col2) OVER (order by Start,Endd DESC) as l2
    ,LAG (Col1) OVER (order by Start,Endd DESC) as l11
    ,LAG (Col2) OVER (order by Start,Endd DESC) as l22
    FROM Example sp   
    order by Start,Endd
)rq
GROUP BY Col1,Col2,case when (rq.l1=Col1 and rq.l2=Col2) or (rq.l11=Col1 and rq.l22=Col2)  then 0 else rank end
order by Start,Endd;

我的目标是合并这些数据以获得以下结果：

但是，正如您在查询结果中所看到的，当我在不同的时间段上具有相同的Col1和Col2值时，合并没有正确完成。它基本上是试图将它们合并在一起，从而为新时期的价值创造问题

---

有人能帮我吗？

您的查询越来越接近，您现在可能已经找到了解决方案。这是一个典型的孤岛和缺口问题。我给出了较长的版本，没有使用超前和滞后。您可以通过使用那些具有密集等级的窗口函数来替换下面45%的代码

DECLARE  @Example TABLE(
Start NVARCHAR(8),
Endd NVARCHAR(8),
Col1 NVARCHAR(2),
Col2 NVARCHAR(2));

INSERT into @Example (Start,Endd,Col1,Col2)
VALUES ('20130801','20140316','02','01'),
('20140317','20140319','04','02'),
('20140320','20140320','04','02'),
('20140321','20140421','02','Z8'),
('20140422','20140429','02','Z9'),
('20140430','20140902','04','02'),
('20140903','20150201','04','02'),
('20150202','20150223','04','02'),
('20150224','20150527','04','02'),
('20150528','99991231','04','02')

SELECT
    TableID=MAX(TableID),Col1=MAX(Col1),Col2=MAX(Col2),Start=MIN(Start),Endd=MAX(Endd)
FROM
(
    SELECT
        TableID,Col1,Col2,Start,Endd,ChangeID=MAX(ChangeOnlyTableID) 
    FROM 
    (
        SELECT
            AllRecords.TableID,AllRecords.Col1,AllRecords.Col2,AllRecords.Start,AllRecords.Endd,ChangeOnlyTableID=ChangesOnly.TableID
        FROM
        (
            SELECT * FROM
            (
                SELECT
                    This.Start,This.Endd,This.TableID,This.Col1,This.Col2,
                    Changed=CASE WHEN (Next.Col1=This.Col1 AND Next.Col2=This.Col2) THEN 0 ELSE 1 END
                FROM
                ( 
                    SELECT TableID=ROW_NUMBER() OVER(ORDER BY Start,Endd,Col1,Col2),Start,Endd,Col1,Col2 FROM @Example 
                )AS This
                LEFT OUTER JOIN
                (
                    SELECT TableID=ROW_NUMBER() OVER(ORDER BY Start,Endd,Col1,Col2),Start,Endd,Col1,Col2 FROM @Example 
                )
                AS Next ON This.TableID=Next.TableID+1
            )
            AS ChangeMarkers
            WHERE Changed=1
        )
        AS AllRecords
        INNER JOIN 
        (
            SELECT * FROM
            (
                SELECT
                    This.Start,This.Endd,This.TableID,This.Col1,This.Col2,
                    Changed=CASE WHEN (Next.Col1=This.Col1 AND Next.Col2=This.Col2) THEN 0 ELSE 1 END
                FROM
                    (
                        SELECT TableID=ROW_NUMBER() OVER(ORDER BY Start,Endd,Col1,Col2),Start,Endd,Col1,Col2 FROM @Example 
                    ) AS This
                    LEFT OUTER JOIN 
                    (
                        SELECT TableID=ROW_NUMBER() OVER(ORDER BY Start,Endd,Col1,Col2),Start,Endd,Col1,Col2 FROM @Example 
                    ) AS Next ON This.TableID=Next.TableID+1
            )
            AS ChangeMarkers
                WHERE Changed=1
        ) 
        AS ChangesOnly ON ChangesOnly.Col1=AllRecords.Col1 AND ChangesOnly.Col2=AllRecords.Col2 AND ChangesOnly.TableID<=AllRecords.TableID
    )AS JoinedResults
    GROUP BY
        TableID,Col1,Col2,Start,Endd
)
AS Final 
GROUP BY 
    Col1,Col2,ChangeID
ORDER BY
    MAX(TableID)

您可以选择使用一些CTE将其稍微缩短，以生成一个查询，例如：

;WITH TableWithIDs AS
( 
    SELECT TableID=ROW_NUMBER() OVER(ORDER BY Start,Endd,Col1,Col2),Start,Endd,Col1,Col2 FROM @Example 
)
,ChangeMarkers AS
(
    SELECT
        This.Start,This.Endd,This.TableID,This.Col1,This.Col2,
        Changed=CASE WHEN (Next.Col1=This.Col1 AND Next.Col2=This.Col2) THEN 0 ELSE 1 END
    FROM
        TableWithIDs AS This
        LEFT OUTER JOIN TableWithIDs AS Next ON This.TableID=Next.TableID+1
)
,ChangesOnly AS
(
    SELECT * FROM ChangeMarkers WHERE Changed=1
)
,
JoinedResults AS
(
    SELECT
        AllRecords.TableID,AllRecords.Col1,AllRecords.Col2,AllRecords.Start,AllRecords.Endd,ChangeOnlyTableID=ChangesOnly.TableID
    FROM
        ChangeMarkers AllRecords
        INNER JOIN ChangesOnly ON ChangesOnly.Col1=AllRecords.Col1 AND ChangesOnly.Col2=AllRecords.Col2 AND ChangesOnly.TableID<=AllRecords.TableID
)

SELECT
    TableID=MAX(TableID),Col1=MAX(Col1),Col2=MAX(Col2),Start=MIN(Start),Endd=MAX(Endd)
FROM
(
    SELECT
        TableID,Col1,Col2,Start,Endd,ChangeID=MAX(ChangeOnlyTableID) 
    FROM 
        JoinedResults
    GROUP BY
        TableID,Col1,Col2,Start,Endd
)
AS Final 
GROUP BY 
    Col1,Col2,ChangeID
ORDER BY
    MAX(TableID)

---

还有一些聪明的黑客可以使用虚拟密钥进一步应用，不过我选择了最直接但更详细的方法。您应该能够通过使用带前置或滞后的密集_排名来改进这一点。您需要发布查询。请阅读并编辑您的问题，将样本数据的相关表格DDL+DML以及您的查询作为文本包含在内。很抱歉，第一次发布：我做了一些修改，带有查询本身的链接。希望这对你来说会更容易！谢谢：我会测试一下，然后回来。虽然到目前为止我还不太熟练，无法用那些lead和lags函数替换您的代码，但我会试着看一看。也许有几把钥匙在哪里？