Alternative to updating every row in my table
select t.*, s.sumTSA
from __SalesDetailInfo t
join ( Select EmpName, sumTSA = SUM(TotalSaleAmount)
       FROM __Sales
       GROUP BY EmpName
     ) as s
ON RTRIM(LTRIM(s.EmpName)) = RTRIM(LTRIM(t.EmpName))


You could use that to create a view.