SELECT MIN(MONTHLY) AS YM, 0 AS MRR FROM MRR_DATA
UNION ALL
SELECT DATE(MONTHLY, '+1 month') AS YM, SUM(IFNULL(NEW_MRR+EXPANSION_MRR-DOWNGRADE_MRR-CHURN_MRR, 0)) OVER (ORDER BY MONTHLY) AS MRR FROM MRR_DATA ORDER BY 1;