SELECT a.ActivityName,SUM( p.RemainderPoints)
FROM activity a left join pointstable p on a.ActivityName =p.ActivityName
WHERE p.UserID =2 AND p.Active = 'TRUE' and a.site ='Site1'
GROUP BY a.ActivityName
Надеюсь, что это поможет!
Пакет RecordLinkage: https://cran.r-project.org/web/packages/RecordLinkage/RecordLinkage.pdf