SQL Server：如何選擇同一組的前2條記錄？

Question

我正在使用SQL Server2008。我有一個問題，我需要獲取由2列Code和Period確定的組中的前2條記錄，然后將它們插入到另一個表中。

這是一個示例表：

Code  |  Period  |  Dept  | DeptWorkPartSum
001      2013-11    D1      53
001      2013-11    D2      33
001      2013-11    D3      12
002      2013-11    D2      30
002      2013-11    D4      28
002      2013-11    D5      15
002      2013-12    D2      100

我想擺脫的是：

Code  |  Period  |  Dept  | DeptWorkPartSum
001      2013-11    D1      53
001      2013-11    D2      33
002      2013-11    D2      30
002      2013-11    D4      28
002      2013-12    D2      100

這可能是一個非常簡單的解決方案，但目前無法確定。

Answer 1

一種簡單的方法是使用具有ROW_NUMBER排名功能的CTE ：

WITH CTE AS
(
    SELECT Code,Period,Dept,DeptWorkPartSum,
           RN = ROW_NUMBER() OVER (PARTITION BY Code,Period, Dept
                                   ORDER BY DeptWorkPartSum)
    FROM dbo.TableName
)
SELECT Code,Period,Dept,DeptWorkPartSum
FROM CTE
WHERE RN <= 2

演示

但是，您期望的結果似乎不正確，因為對於所有這三個代碼， Dept均不同。

也許您不想按Dept分組而是按Dept分組，那么結果是正確的：

WITH CTE AS
(
    SELECT Code,Period,Dept,DeptWorkPartSum,
           RN = ROW_NUMBER() OVER (PARTITION BY Code,Period
                                   ORDER BY Dept, DeptWorkPartSum)
    FROM dbo.TableName
)
SELECT Code,Period,Dept,DeptWorkPartSum
FROM CTE
WHERE RN <= 2

演示

Answer 2

SELECT Code, Period, Dept, DeptWorkPartSum
FROM (
  SELECT Code, Period, Dept, DeptWorkPartSum
    ,ROW_NUMBER ( ) OVER ( PARTITION BY Code, Period, Dept ORDER BY DeptWorkPartSum DESC) r
  FROM table) q
WHERE r <= 2

Answer 3

try this:


with cte as
(
select *,ROW_NUMBER() over (partition by Code,Period,Dept order by Code) as rn from table
)

select Code,Period,Dept,DeptWorkPartSum from cte where rn<=2 

小提琴演示