Recursive CTE trouble - sql-server

Question

I'm having some trouble coming up with the CTE way of doing a task. I already have a loop method and it is fast enough, but I wanted to do it in a proper way to better learn and understand CTE usage.
SQL:
DECLARE #Income MONEY=125000.00,
#Active INT=0,
#Year CHAR(4)='2018'
DECLARE #T TABLE ([Year] CHAR(4),Active INT,UpperLimit MONEY,Factor DECIMAL(6,3))
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,5000.0,1.00;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,100000.0,0.85;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,500000.0,0.80;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,999999999.0,0.75;
WITH GradientCTE ([Year], Active, UpperLimit, Factor,[Income],WeightedValue,[Row])
AS
(
SELECT [Year], Active, UpperLimit, Factor
,#Income AS [Income]
,CAST(0.0 AS DECIMAL(16,3))AS WeightedValue
,ROW_NUMBER() OVER(PARTITION BY [Year],Active ORDER BY UpperLimit ASC) AS [Row]
From #T
)
SELECT *
FROM GradientCTE
ORDER BY UpperLimit
TLDR version; current output:
Year Active UpperLimit Factor Income WeightedValue Row
2018 0 5000.000 1.000 125000.000 0.000 1
2018 0 100000.000 0.850 125000.000 0.000 2
2018 0 500000.000 0.800 125000.000 0.000 3
2018 0 999999999.000 0.750 125000.000 0.000 4
What I would like:
Year Active UpperLimit Factor Income WeightedValue Row
2018 0 5000.000 1.000 125000.000 5000.000 1
2018 0 100000.000 0.850 120000.000 85000.000 2
2018 0 500000.000 0.800 20000.000 16000.000 3
2018 0 999999999.000 0.750 0.000 0.000 4
Explained:
Currently, the looping logic goes over the set row by row and reduces #Income by the UpperLimit for each row until no money is left. It uses that to multiply that amount by the Factor to get a weighted amount. So, in the example provided, the starting income is 125,000.00. The first 5000 are at full weight (1.00), so we reduce the income by 5000 and move the the next row saving the summed weighted value. This is done until income is 0. So, 125,000 should come out to (5000 * 1.0) + (100000 * 0.85) + (20000 * 0.80) + (0.00 * 0.75) or 106,000 total if summed.

Answer 1

Thanks to Ross Bush's answer, it led me down the right track to solve the problem. From a maintenance standpoint, I think a looping pattern is easier to understand, so I likely won't implement the CTE version and performance isn't an issue as the data set is tiny.
DECLARE #Income DECIMAL(18,3)=125000.00,
#Active INT=0,
#Year CHAR(4)='2018'
DECLARE #T TABLE ([Year] CHAR(4),Active INT,UpperLimit DECIMAL(18,3),Factor DECIMAL(18,3))
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,5000.0,1.00;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,100000.0,0.85;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,500000.0,0.80;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,999999999.0,0.75;
;WITH GradientCTE
AS
(
SELECT DISTINCT
[YEAR],Active,UpperLimit=0.00, Factor = 0.00, [Row] = 0
FROM #T
UNION ALL
SELECT [Year],Active,UpperLimit, Factor
,ROW_NUMBER() OVER(PARTITION BY [Year],Active ORDER BY UpperLimit ASC) AS [Row]
From #T
)
,Reduce AS (
SELECT
[YEAR],Active,CAST(#Income AS DECIMAL(18,3)) AS [RemainingIncome],
Row,
Factor
,UpperLimit
,CAST(0.00 AS DECIMAL(18,3)) AS WeightedValue
FROM GradientCTE
WHERE UpperLimit=0
UNION ALL
SELECT
g.[YEAR],g.Active,CASE WHEN CAST([RemainingIncome] - G.UpperLimit AS DECIMAL(18,3)) < 0 THEN 0 ELSE CAST([RemainingIncome] - G.UpperLimit AS DECIMAL(18,3)) END AS [RemainingIncome],
G.Row,
g.Factor
,g.UpperLimit
,CAST(CASE WHEN [RemainingIncome]>G.UpperLimit THEN G.UpperLimit * G.Factor ELSE R.[RemainingIncome] * G.Factor END AS DECIMAL(18,3)) AS WeightedValue
FROM GradientCTE G
INNER JOIN Reduce R ON R.Row = G.Row -1
AND g.Year=r.Year
AND g.Active=r.Active
)
SELECT
*
-- [Year],Active,SUM(WeightedValue)
FROM Reduce
WHERE [RemainingIncome] >= 0
--GROUP BY [Year],Active

Answer 2

You can reduce the results within another CTE, recursively. I added a UNION with 0 to in the first set to produce the first line showing the starting income.
DECLARE #Income DECIMAL(18,3)=125000.00,
#Active INT=0,
#Year CHAR(4)='2018'
DECLARE #T TABLE ([Year] CHAR(4),Active INT,UpperLimit DECIMAL(18,3),Factor DECIMAL(18,3))
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,5000.0,1.00;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,100000.0,0.85;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,500000.0,0.80;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT '2018',0,999999999.0,0.75;
;WITH GradientCTE
AS
(
SELECT ReduceAmount = 0, UpperLimit=0.00, Factor = 0.00, Row = 0
UNION ALL
SELECT ReduceAmount = UpperLimit * Factor, UpperLimit, Factor
,ROW_NUMBER() OVER(PARTITION BY [Year],Active ORDER BY UpperLimit ASC) AS [Row]
From #T
)
,Reduce AS (
SELECT
Income = CAST(#Income AS DECIMAL(18,3)),
Row,
ReduceAmount
FROM GradientCTE
WHERE ReduceAmount=0
UNION ALL
SELECT
Income = CASE WHEN CAST(Income - G.ReduceAmount AS DECIMAL(18,3)) < 0 THEN 0 ELSE CAST(Income - G.ReduceAmount AS DECIMAL(18,3)) END,
G.Row,
G.ReduceAmount
FROM GradientCTE G
INNER JOIN Reduce R ON R.Row = G.Row -1
)
SELECT * FROM Reduce
WHERE
Income >= 0

Answer 3

DECLARE #Income MONEY=125000.00,
#Active INT=0,
#Year CHAR(4)='2018',
#vIncome Money = 0
DECLARE #T TABLE ([Year] CHAR(4),Active INT,UpperLimit MONEY,Factor
DECIMAL(6,3))
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT
'2018',0,5000.0,1.00;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT
'2018',0,100000.0,0.85;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT
'2018',0,500000.0,0.80;
INSERT INTO #T ([Year],Active,UpperLimit,Factor) SELECT
'2018',0,999999999.0,0.75;
Select * ,ROW_NUMBER() OVER(PARTITION BY [Year],Active ORDER BY
UpperLimit ASC) AS [Row],CAST(0.0 AS DECIMAL(16,3))AS Income,CAST(0.0 AS
DECIMAL(16,3))AS WeightedValue
into #tmp from #T t1
--Select (t2.UpperLimit * t2.Factor),t2.*,t1.Row as prev,t1.UpperLimit
--from #tmp t1
--inner join #tmp t2 on (t1.Row = t2.Row +1)
update t2
set
#vIncome = #Income,
#Income = case when (#Income > t2.UpperLimit) then
#Income - t2.UpperLimit
else
0
end,
t2.Income = #Income,
t2.WeightedValue = case when (#vIncome > t2.UpperLimit) then
(t2.UpperLimit * t2.Factor)
else
#vIncome *t2.Factor
end
from #tmp t1
inner join #tmp t2 on (t1.Row = t2.Row +1)
Select * from #tmp
drop table #tmp