问SQL While循环中的算法

EN

DECLARE @startyear INT = 2016, @endyear INT = 2080, @cycle VARCHAR(9) = '4-6-6-6-6';

WITH CTE1 AS (
    SELECT SUBSTRING(@cycle, A.B, 1) S, ROW_NUMBER() OVER (ORDER BY A.B) RN
    FROM (
        VALUES (1), (3), (5), (7), (9)) A(B))
, E1(N) AS (SELECT 1 FROM (VALUES (1), (1), (1), (1), (1), (1), (1), (1), (1), (1)) A(B))
, E2(N) AS (SELECT 1 FROM E1 A CROSS JOIN E1)
, CTE2 AS (
    SELECT CAST(CTE1.S AS INT) S, (E2.N - 1) * 5 + RN RN
    FROM CTE1
    CROSS JOIN (SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E2) E2(N)
    WHERE E2.N <= (SELECT (@endyear - @startyear) / SUM(CAST(S AS INT)) + 1 FROM CTE1))
SELECT @startyear + SUM(T2.S) Years
FROM CTE2 T1
JOIN CTE2 T2 ON T1.RN >= T2.RN
GROUP BY T1.RN
HAVING @startyear + SUM(T2.S) < @endyear
ORDER BY T1.RN;