Prøv dette:
;WITH Subtotals
AS
(
SELECT
T1.Id, T1.CodeId, SUM(T2.Value) SubTotal
FROM Tb1 T1
JOIN Tb1 T2
ON T1.CodeId = T2.CodeId
AND T1.Id >= T2.Id
GROUP BY T1.Id, T1.CodeId
)
SELECT
S.ID,
S.CodeID,
T1.Value,
CASE WHEN T2.value >= S.Subtotal
THEN T1.value
ELSE T1.value - (S.Subtotal - T2.value)
END UsedValue,
T2.Value T2Value
FROM Subtotals S
JOIN Tb2 T2
ON S.CodeId = T2.CodeId
JOIN Tb1 T1
ON S.Id = T1.Id
WHERE T2.Value >= S.SubTotal - T1.Value
Se resultat på SQL FIDDLE