sql - 从具有公共(public)列的记录集中获取最大值

Question

根据下面的记录集，我有三列，需要返回每组 PersonId 的最大 CaseId 值。

ID    PersonId  CaseId
66    30        410
1681  30        3508
226   31        958
856   31        2213
1023  31        2400

例如，我想返回一个记录集，例如:

ID    PersonId  CaseId
1681  30        3508
1023  31        2400

如您所见，我始终返回所有 PersonId 集的最大 CaseId。

我尝试了以下方法，但它并不总是返回最大记录:

WITH latestRecord AS
 (
  SELECT  CaseId, PersonId, ID,
    ROW_NUMBER() OVER (PARTITION BY PersonId ORDER BY ID ASC) AS RN
  FROM    Employee
  )
  SELECT  Max(RN),CaseId, PersonId
  FROM    latestRecord
  GROUP BY RN,CaseId, PersonId
  --WHERE   RN > 1
  ORDER BY CaseId

感谢您的帮助!

Answer 1

你几乎是对的:

WITH latestRecord
AS
(
    SELECT  CaseId, 
            PersonId, 
            ID,
            RN=ROW_NUMBER() OVER (PARTITION BY PersonId ORDER BY CaseId DESC) 
    FROM    Employee
)
SELECT  CaseId, 
        PersonId, 
        ID
FROM    latestRecord
WHERE   RN = 1
ORDER BY CaseId