A recursive statement or a statement using numbers table are probably the first two options:
Table:
SELECT *
INTO Data
FROM (VALUES
(CONVERT(date, '20-12-2021', 105), 200, 2, 100),
(CONVERT(date, '21-12-2021', 105), 150, 4, 101)
) v (Date, Quantity, RollCount, PlanID)
Statement with recursion:
; WITH rCTE AS (
SELECT d.Date, d.Quantity, 1 AS RollNo, d.RollCount, d.PlanID
FROM Data d
UNION ALL
SELECT r.Date, r.Quantity, r.RollNo + 1, r.RollCount, r.PlanID
FROM rCTE r
WHERE r.RollNo + 1 <= r.RollCount
)
SELECT Date, (Quantity * 1.0 / RollCount) AS Quantity, RollNo, PlanID
FROM rCTE
ORDER BY PlanID, RollNo
OPTION (MAXRECURSION 0)
Statement using numbers table (with 1000 rows):
; WITH nCTE AS (
SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS Rn
FROM (VALUES (1), (1), (1), (1), (1), (1), (1), (1), (1), (1)) a (n)
CROSS APPLY (VALUES (1), (1), (1), (1), (1), (1), (1), (1), (1), (1)) b (n)
CROSS APPLY (VALUES (1), (1), (1), (1), (1), (1), (1), (1), (1), (1)) c (n)
)
SELECT d.Date, (d.Quantity * 1.0 / d.RollCount) AS Quantity, n.Rn AS RollNo, d.PlanID
FROM Data d
JOIN nCTE n ON d.RollCount >= n.Rn
ORDER BY d.PlanID, n.Rn
Result:
Date Quantity RollNo PlanID
2021-12-20 100.000000000000 1 100
2021-12-20 100.000000000000 2 100
2021-12-21 37.500000000000 1 101
2021-12-21 37.500000000000 2 101
2021-12-21 37.500000000000 3 101
2021-12-21 37.500000000000 4 101