T1 RecNo T2 Recno T3 Recno T2 Amount T3 Amount 1 1 1 50 10 1 2 1 60 10 1 3 1 40 10 1 1 2 50 15 1 2 2 60 15 1 3 2 40 15 SUM 300 75A GROUP BY will not change this, it will only hide the actual records produced in the JOIN. Perhaps the following SELECT will be more appropriate for the job;
SELECT T1.Id, T2.Id, SUM(T2.Amount) ; FROM T1 INNER JOIN T2 ON T1.ID = T2.Fid ; UNION ALL ; SELECT T1.ID, T3.Id, SUM(T3.Amount) ; FROM T1 INNER JOIN T3 ON T1.ID = T3.Fid ...