with a as (select MONTHLY, NEW_MRR +EXPANSION_MRR -DOWNGRADE_MRR - CHURN_MRR as one from MRR_DATA order by MONTHLY)
select MONTHLY as YM, ifnull(sum, 0) as MRR
from 
(select a1.MONTHLY, a1.one, sum(a2.one) as sum
FROM   a a1
left outer JOIN a a2
ON  a1.MONTHLY > a2.MONTHLY
GROUP BY a1.MONTHLY,a1.one
ORDER BY a1.MONTHLY)
order by YM