я думаю, что вы можете просто использовать группу как
SELECT DESCRIPTION_,DISPLAYNAME
,SUM(IIF(FINISHDATETIME IN (GETDATE()-4),SUCCESFULRECORDCOUNT,0)) AS 'DAY1'
,SUM(IIF(FINISHDATETIME IN (GETDATE()-3),SUCCESFULRECORDCOUNT,0)) AS 'DAY2'
,SUM(IIF(FINISHDATETIME IN (GETDATE()-2),SUCCESFULRECORDCOUNT,0)) AS 'DAY3'
,SUM(IIF(FINISHDATETIME IN (GETDATE()-1),SUCCESFULRECORDCOUNT,0)) AS 'DAY4'
FROM LOGTABLE (NOLOCK)
GROUP BY
DESCRIPTION_,
DISPLAYNAME