Question

我有一张包含历史信息的表格，如下所示。

表A

switchMap

表B

ID    Set_Date  Reason     pk
 1      1/1/17   denied    1
 1      1/2/17   approved  2

当set_date介于startDate和EndDate

之间时，我需要最新的值

示例：

StartDate    EndDate    ID
  1/1/17      1/2/17     1

有没有更简单的方法来提取我所要求的内容？

最终结果应为：

SELECT * 
  FROM(
SELECT *, DENSE_RANK() OVER (PARTITION BY ID ORDER BY SET_DATE DESC) AS RNK
FROM TableB B
INNER JOIN TABLEA ON B.ID = A.ID 
  AND A.SET_DATE BETWEEN B.STARTDATE AND B.ENDDATE
    --BUT TWO VALUES APPLY HERE AND I ONLY WANT ONE VALUE, THE LATEST ENTRY OF THE SET OF DATA THAT FALLS BETWEEN THE TWO DATES. SO IS THE BEST APPROACH TO ADD A RNK AND SUBQUERY?
              )
WHERE 1=1
  AND RNK = 1

Answer 1

一种方法是使用FIRST_VALUE窗口函数。

SELECT DISTINCT A.ID, FIRST_VALUE(A.REASON) OVER (PARTITION BY A.ID ORDER BY A.SET_DATE DESC) AS Reason
FROM TableB B
INNER JOIN TABLEA A ON B.ID = A.ID 
AND A.SET_DATE BETWEEN B.STARTDATE AND B.ENDDATE

在日期之间排名

1 个答案: