从组中选择最新日期

Question

I need to find the latest Appeal date for each record in our database, I've tried using Max(date) but it still gives me all of our Constituents rater than just the one row of the latest date I'm using MS SQL

    SELECT 
    [Constituent ID]
      ,[Assigned Appeal Category]
      ,[Assigned Appeal ID]**strong text**
      ,[Assigned Appeal Response]
      ,MAX([Assigned Appeal Date])


  FROM [FHF_MarketingData].[dbo].[FHF_Constituent_Appeals]

  WHERE [Assigned Appeal Category] = 'TELEMARKETING'



GROUP BY 
    [Constituent ID],
    [Assigned Appeal Category],
    [Assigned Appeal ID],
    [Assigned Appeal Response],
    [Assigned Appeal Date]

Answer 1

You can use ROW_NUMBER() and TOP (1) WITH TIES for this:

SELECT TOP (1) WITH TIES ca.*
FROM [FHF_MarketingData].[dbo].[FHF_Constituent_Appeals] ca
WHERE ca.[Assigned Appeal Category] = 'TELEMARKETING'
ORDER BY ROW_NUMBER() OVER (PARTITION BY [Constituent ID] ORDER BY [Assigned Appeal Date] DESC);

This assumes that you really mean for each constituent, not for each record.

Another method that might even have better performance with the right indexes is:

SELECT ca.*
FROM [FHF_MarketingData].[dbo].[FHF_Constituent_Appeals] ca
WHERE ca.[Assigned Appeal Category] = 'TELEMARKETING' AND
      ca.[Assigned Appeal Date] = (SELECT MAX(ca2.[Assigned Appeal Date])
                                   FROM [FHF_MarketingData].[dbo].[FHF_Constituent_Appeals] ca2
                                   WHERE ca2.[Constituent ID] = ca.[Constituent ID] AND
                                         ca2.[Assigned Appeal Category] = ca.[Assigned Appeal Category]
                                  );

Answer 2

Without sample data I cant say for sure this is the correct answer but I would approach it by grabbing the max date based on the ID you are interested in and inner joining it as a sub query. Swap out the sub query ID if you need Appeal ID instead.

 SELECT [Constituent ID]
        ,[Assigned Appeal Category]
        ,[Assigned Appeal ID]
        ,[Assigned Appeal Response]
        ,MaxDt
    FROM [FHF_MarketingData].[dbo].[FHF_Constituent_Appeals] CA
    INNER JOIN (
        SELECT  MAX([Assigned Appeal Date]) MaxDT
            ,[Constituent ID]
        FROM [FHF_MarketingData].[dbo].[FHF_Constituent_Appeals]
        WHERE [Assigned Appeal Category] = 'TELEMARKETING'
        GROUP BY [constituent id]
        ) MaxDt ON MaxDt.[Constituent ID] = CA.[Constituent ID]