WITH MRRTable as
(
    SELECT
    *
    FROM
    MRR_DATA
    LEFT JOIN
    (
        SELECT 
        date(datetime(MONTHLY,'+1 months')) AS MONTHLY,
        NEW_MRR + EXPANSION_MRR - DOWNGRADE_MRR - CHURN_MRR AS 前月計算結果
        FROM MRR_DATA
        GROUP BY MONTHLY
    ) a ON a.MONTHLY = MRR_DATA.MONTHLY
),
MRRTable2 as(
    SELECT
    MRRTable.MONTHLY AS YM,
    (case 
    when MRRTable.前月計算結果 IS NULL THEN 0
    else SUM(MRRTable.前月計算結果) OVER(ORDER BY MRRTable.MONTHLY)
    END) AS MRR
    FROM
    MRRTable
)

SELECT
*
FROM
MRRTable2
ORDER BY YM ASC