SELECT N.MONTHLY AS YM, SUM(IFNULL(P.NEW_MRR+P.EXPANSION_MRR-P.DOWNGRADE_MRR-P.CHURN_MRR, 0)) OVER (ORDER BY N.MONTHLY) AS MRR FROM MRR_DATA N LEFT JOIN MRR_DATA P ON DATE(N.MONTHLY, '-1 month') = P.MONTHLY ORDER BY 1;