如何根據另一列中的值找到最大值？ SQL

Question

我有一張桌子

Repcode  ID     LastUpdateDate
ABCD     ADAMA  12/6/2019
EFG      ERINA  13/6/2019
ABCD     ADAMA  14/6/2019
TOM      TERRY  12/4/2019
SAM      SAMMY  12/6/2019
TOM      SLIPP  24/10/2013
ABCD     BALLP  22/4/2010

對於每個Repcode，我需要基於LastUpdateDate的最新ID。 每個RepCode一行

Repcode ID      LastUpdateDate
ABCD    ADAMA   14/6/2019
EFG     ERINA   13/6/2019
SAM     SAMMY   12/6/2019
TOM     TERRY   12/4/2019

Repcode被重用，因此基礎ID可能會隨時間變化。

WITH summary AS (
  SELECT m.*,
         ROW_NUMBER() OVER(ORDER BY m.lastupdatedate DESC) AS rank
    FROM Mtable m
    )

SELECT distinct s.repCode, s.id, LastUpdateDate
  FROM summary s

但是我沒有得到像我期望的那樣的簡明結果，只是基於最大lastupdatedate的最新repcode / id。 請幫助，提前謝謝！！！

Answer 1

您不想select distinct 。 您需要一個where子句和一個PARTITION BY子句：

WITH summary AS (
      SELECT m.*,
             ROW_NUMBER() OVER (PARTITION BY m.repcode ORDER BY m.lastupdatedate DESC) AS rank
      FROM Mtable m
     )
SELECT s.repCode, s.id, LastUpdateDate
FROM summary s
WHERE rank = 1;

Answer 2

有不存在：

select s.*
from summary s
where not exists (
  select 1 from summary
  where repcode = s.repcode and lastupdatedate > s.lastupdatedate
)

Answer 3

您可以嘗試在最大范圍內使用內部聯接

select  m.* 
from  Mtable m
inner join  (

  select  Repcode, ID, max(LastUpdateDate ) max_date 
  from  Mtable 
  group by   Repcode, ID 

  ) t on t.Repcode = m.Repcode 
        and t.id = m.id     
          and t.max_date  = m.LastUpdateDate 

Answer 4

使用GROUP BY和HAVING子句：

SELECT * FROM summary GROUP BY Repcode HAVING MAX(LastUpdateDate)