Question

I thought I had it but it seemed I was wrong.

I have a query

select PrestatieCode, Uitvoerdatum, Identificatie, Foutmelding 
from bam_Zending_AllInstances as zAll
left outer join bam_Zending_CompletedRelationships as zRel on 
zAll.ActivityID = zRel.ActivityID
left outer join bam_Prestatie_AllInstances as pAll on 
zRel.ReferenceData = pAll.ActivityID
where zAll.Zender = 'BL15' 
and ReferenceType = 'Activity' 
and Zendingnummer = '632'

This shows a list of PrestatieCodes, also duplicates.
Now I only need to have a list of PretatieCodes without the duplicates, it should just pick the one with the lastest date. The datecolumn = Uitvoerdatum.

I thought I’d try something like:

select max(Uitvoerdatum), PrestatieCode  
from bam_Zending_AllInstances as zAll
left outer join bam_Zending_CompletedRelationships as zRel on 
zAll.ActivityID = zRel.ActivityID
left outer join bam_Prestatie_AllInstances as pAll on 
zRel.ReferenceData = pAll.ActivityID
where zAll.Zender = 'BL15' 
and ReferenceType = 'Activity' 
and Zendingnummer = '632'
group by PrestatieCode

which gives me what I want. However as you can notice it does not have the 2 columns “Identificatie” and Foutmelding. If I add these it gives me the error

Column 'bam_Prestatie_AllInstances.Identificatie' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

So I’m guessing my approach is wrong. I need to see all the columns but only for the latest “PrestatieCode”s.

Am I making any sense?

Answer 1

Without any schema it is a tad difficult. But what you need to try is getting the id and max value (so in your case PrestatieCode and MAX(Uitvoerdatum) and then do a sub join)

SELECT  YourTabel.*
FROM    YourTabel INNER JOIN
        (
            SELECT  PrestatieCode,
                    MAX(Uitvoerdatum) MaxDates
            FROM    YourTabel
            WHERE   YourCondition
            GROUP BY PrestatieCode 
        ) YourTableMaxDates ON  YourTabel.PrestatieCode = YourTableMaxDates.PrestatieCode
                            AND YourTabel.Uitvoerdatum = YourTableMaxDates.MaxDates

This should get you the latest data per PrestatieCode