Running Total in SqlServer

SELECT a.Id, a.sal, (SELECT SUM(b.sal)
                       FROM tbl_Testing b
                       WHERE b.id <= a.id) as Total
FROM   tbl_Testing a
ORDER BY a.id;

 Running Total Based on Multiple Columns

select *,(select sum(Credit)-sum(Debit) from Transactions where Tid<=t.Tid)
as Balance from Transactions as t