Question

我有一个名为tblHumanResources的表，我想在其中获取行的集合，其中包含每个不同empID的最新2行。（最新的effectiveDate）。

场景：我希望按empID排序条目集合，然后每个empID获得2行，其中包含最新的effectiveDate（如果按降序排序，则为effectiveDate的前2位）。

注意：我使用的是SQL Server 2008，我的表有数千行。

tblHumanResources表

| empID | effectiveDate |  Company | Description
| 0-123 |    1999-04-18 | DFD Comp | Analyst
| 0-234 |    2007-04-22 | ABC Comp | Manager
| 0-222 |    2012-02-19 | CDC Comp | Janitor
| 0-213 |    2009-05-03 | CBB Comp | Teller
| 0-223 |    2012-01-23 | CBB Comp | Teller
| 0-223 |    1999-05-27 | CBB Comp | Teller
| 0-123 |    2014-01-25 | DFD Comp | Analyst
| 0-234 |    1999-01-23 | ABC Comp | Manager
| 0-222 |    2014-12-13 | CDC Comp | Janitor
| 0-213 |    2014-02-12 | CBB Comp | Teller
| 0-223 |    2005-03-26 | CBB Comp | Teller
| 0-123 |    2005-02-05 | DFD Comp | Analyst
| 0-234 |    2014-05-18 | ABC Comp | Manager
| 0-222 |    2001-06-23 | CDC Comp | Janitor
| 0-213 |    2003-05-12 | CBB Comp | Teller

//and so on...

我想要显示如下内容：

| empID | effectiveDate |  Company | Description
| 0-123 |    2014-01-25 | DFD Comp | Analyst
| 0-123 |    2005-02-05 | DFD Comp | Analyst
| 0-213 |    2014-02-12 | CBB Comp | Teller
| 0-213 |    2009-05-03 | CBB Comp | Teller
| 0-222 |    2014-12-13 | CDC Comp | Janitor
| 0-222 |    2012-02-19 | CDC Comp | Janitor
| 0-223 |    2012-01-23 | CBB Comp | Teller
| 0-223 |    2005-03-26 | CBB Comp | Teller
| 0-234 |    2014-05-18 | ABC Comp | Manager
| 0-234 |    2007-04-22 | ABC Comp | Manager

//and so on...

非常感谢任何帮助。

PS：我现在无法尝试你的代码，因为我的开发笔记本电脑不适合我。我会在几个小时后尝试您的答案，以便能够正确选择解决问题的答案。

谢谢。

Answer 1

使用子查询

SELECT empID , effectiveDate ,  Company , [Description] 
FROM 
  (
    SELECT empID , effectiveDate ,  Company , [Description]
      , ROW_NUMBER() OVER (PARTITION BY empID ORDER BY effectiveDate DESC) rn
    FROM TableName
   ) A 
WHERE rn <= 2

使用CTE

;WITH CTE 
AS
  (
    SELECT empID , effectiveDate ,  Company , [Description]
      , ROW_NUMBER() OVER (PARTITION BY empID ORDER BY effectiveDate DESC) rn
    FROM TableName
  ) 
SELECT  empID , effectiveDate ,  Company , [Description] 
FROM CTE
WHERE rn <= 2

不使用排名功能

SELECT t1.empID 
      ,t1.effectiveDate 
      ,t1.Company 
      ,t1.[Description]
FROM TableName t1
WHERE t1.effectiveDate IN (SELECT TOP 2 effectiveDate 
                           FROM TableName 
                           WHERE empID = t1.empID
                           ORDER BY effectiveDate DESC)

为SQL中的列中的每个不同字段选择包含2个最新行的所有行

1 个答案: