Sql 在（分区依据…）上使用行数（）时出现问题

我正在使用SQLServer2008R2。我有一个名为EmployeeHistory的表，其中包含以下结构和示例数据：

EmployeeID Date      DepartmentID SupervisorID
10001      20130101  001          10009
10001      20130909  001          10019
10001      20131201  002          10018
10001      20140501  002          10017
10001      20141001  001          10015
10001      20141201  001          10014

请注意，随着时间的推移，员工10001已经更换了两个部门和几个主管。我想做的是，按日期字段列出该员工在每个部门的工作开始和结束日期。因此，输出将如下所示：

EmployeeID DateStart DateEnd  DepartmentID 
10001      20130101  20131201 001
10001      20131201  20141001 002
10001      20141001  NULL     001

;WITH x 
 AS (SELECT *, 
            Row_number() 
              OVER( 
                partition BY employeeid 
                ORDER BY datestart) rn 
     FROM   employeehistory) 
SELECT * 
FROM   x x1 
   LEFT OUTER JOIN x x2 
                ON x1.rn = x2.rn + 1 

我打算使用下面的查询对数据进行分区，但失败了。部门从001更改为002，然后再返回001。显然我不能按部门ID分区。。。我肯定我忽略了显而易见的事实。有什么帮助吗？提前谢谢你

SELECT * ,ROW_NUMBER() OVER (PARTITION BY EmployeeID, DepartmentID
ORDER BY [Date]) RN FROM EmployeeHistory

---

我会这样做：

EmployeeID DateStart DateEnd  DepartmentID 
10001      20130101  20131201 001
10001      20131201  20141001 002
10001      20141001  NULL     001

;WITH x 
 AS (SELECT *, 
            Row_number() 
              OVER( 
                partition BY employeeid 
                ORDER BY datestart) rn 
     FROM   employeehistory) 
SELECT * 
FROM   x x1 
   LEFT OUTER JOIN x x2 
                ON x1.rn = x2.rn + 1 

---

或者可能是x2.rn-1。你得看看。在任何情况下，你都明白了。一旦将表本身连接起来，就可以进行筛选、分组、排序等操作，以获得所需的内容。

有点复杂。最简单的方法是引用我为您创建的，生成精确结果的方法。出于性能或其他方面的考虑，您可以通过一些方法来改进它，但希望这至少比其他方法更清晰

要点是，首先获得数据的标准排名，然后使用该排名将数据分为多个组，然后为每个组找到结束日期，然后删除任何中间行。行数和交叉应用在易读性方面有很大帮助

编辑2019：

事实上，出于某种原因，SQL Fiddle看起来确实坏了，但在SQL Fiddle站点上似乎是个问题。以下是刚刚在SQL Server 2016上测试的完整版本：

CREATE TABLE Source
(
  EmployeeID int,
  DateStarted date,
  DepartmentID int
)

INSERT INTO Source
VALUES
(10001,'2013-01-01',001),
(10001,'2013-09-09',001),
(10001,'2013-12-01',002),
(10001,'2014-05-01',002),
(10001,'2014-10-01',001),
(10001,'2014-12-01',001)


SELECT *, 
  ROW_NUMBER() OVER (PARTITION BY EmployeeID ORDER BY DateStarted) AS EntryRank,
  newid() as GroupKey,
  CAST(NULL AS date) AS EndDate
INTO #RankedData
FROM Source
;

UPDATE #RankedData
SET GroupKey = beginDate.GroupKey
FROM #RankedData sup
  CROSS APPLY 
  (
    SELECT TOP 1 GroupKey
    FROM #RankedData sub 
    WHERE sub.EmployeeID = sup.EmployeeID AND
      sub.DepartmentID = sup.DepartmentID AND
      NOT EXISTS 
        (
          SELECT * 
          FROM #RankedData bot 
          WHERE bot.EmployeeID = sup.EmployeeID AND
            bot.EntryRank BETWEEN sub.EntryRank AND sup.EntryRank AND
            bot.DepartmentID <> sup.DepartmentID
        )
      ORDER BY DateStarted ASC
    ) beginDate (GroupKey);

UPDATE #RankedData
SET EndDate = nextGroup.DateStarted
FROM #RankedData sup
  CROSS APPLY 
  (
    SELECT TOP 1 DateStarted
    FROM #RankedData sub
    WHERE sub.EmployeeID = sup.EmployeeID AND
      sub.DepartmentID <> sup.DepartmentID AND
      sub.EntryRank > sup.EntryRank
    ORDER BY EntryRank ASC
  ) nextGroup (DateStarted);

SELECT * FROM 
(
SELECT *, ROW_NUMBER() OVER (PARTITION BY GroupKey ORDER BY EntryRank ASC) AS GroupRank FROM #RankedData
) FinalRanking
WHERE GroupRank = 1
ORDER BY EntryRank;

DROP TABLE #RankedData
DROP TABLE Source

---

这似乎是一个常见的缺口和孤岛问题。行号rn1和rn2的两个序列之间的差异给出了组号

逐个CTE运行此查询，并检查中间结果以了解其工作原理

样本数据

我对问题中的样本数据进行了一些扩展

DECLARE @Source TABLE
(
    EmployeeID int,
    DateStarted date,
    DepartmentID int
)

INSERT INTO @Source
VALUES
(10001,'2013-01-01',001),
(10001,'2013-09-09',001),
(10001,'2013-12-01',002),
(10001,'2014-05-01',002),
(10001,'2014-10-01',001),
(10001,'2014-12-01',001),

(10005,'2013-05-01',001),
(10005,'2013-11-09',001),
(10005,'2013-12-01',002),
(10005,'2014-10-01',001),
(10005,'2016-12-01',001);

查询SQL Server 2008

SQLServer2008中没有LEAD函数，因此我必须通过outerApply使用self-join来获取DateEnd的下一行的值

查询SQL Server 2012+

从SQL Server 2012开始，有一个LEAD功能可以提高此任务的效率

WITH
CTE
AS
(
    SELECT
        EmployeeID
        ,DateStarted
        ,DepartmentID
        ,ROW_NUMBER() OVER (PARTITION BY EmployeeID ORDER BY DateStarted) AS rn1
        ,ROW_NUMBER() OVER (PARTITION BY EmployeeID, DepartmentID ORDER BY DateStarted) AS rn2
    FROM @Source
)
,CTE_Groups
AS
(
    SELECT
        EmployeeID
        ,MIN(DateStarted) AS DateStart
        ,DepartmentID
    FROM CTE
    GROUP BY
        EmployeeID
        ,DepartmentID
        ,rn1 - rn2
)
SELECT
    CTE_Groups.EmployeeID
    ,CTE_Groups.DepartmentID
    ,CTE_Groups.DateStart
    ,LEAD(CTE_Groups.DateStart) OVER (PARTITION BY CTE_Groups.EmployeeID ORDER BY CTE_Groups.DateStart) AS DateEnd
FROM
    CTE_Groups
ORDER BY
    EmployeeID
    ,DateStart
;

结果

---

两年多后，@coding_idiot，但我已经通过一个完整的脚本对其进行了更正，以便在您自己的服务器上运行。@DominicP，我认为可以用一种更简单、更高效的方式完成。看看我的答案。