CTE Recursive Running Total.sql

/*
  Using a CTE, we can iterate through to get the previous row in order to calculate and keep
  a running total
*/
WITH PrevRow
     AS (SELECT Acolumn,
                Bcolumn,
                HoldingColumn = Bcolumn,
                RunningTotal = HoldingColumn
         FROM   Atable
         WHERE  ConditionColumn = 0
         UNION ALL
         SELECT A.N,
                A.B,
                E = A.B * ( 1 - PrevRow.RunningTotal ),
                RunningTotal = A.B * ( 1 - PrevRow.RunningTotal ) + PrevRow.RunningTotal
         FROM   PrevRow
                JOIN A
                  ON A.N = R.N + 1)
SELECT N,
       B,
       E = CAST(E AS DECIMAL(10,9))
FROM   PrevRow