Dear @RPA,
Try the below query, it might be helpful.
SELECT Id, SUM(T1) as T1, SUM(T2) as T2, SUM(T3) as T3 FROM
(SELECT Id, T1, T2,T3 FROM Tbl UNION ALL SELECT Id, Tb1, Tb2, Tb3 FROM Tbl1) T
GROUP BY Id
OR
SELECT Id, SUM(T1) as T1, SUM(T2) as T2, SUM(T3) as T3 FROM
(SELECT Id, T1, T2,T3 FROM Tbl UNION ALL SELECT Id,Tb1 as T1, Tb2 as T2, Tb3 as T3 FROM Tbl1) T
GROUP BY Id
cheers...