select
	MRR.MONTHLY as YM,
	SUM(IFNULL(MRR_BF.MRR, 0)) as MRR
from
	(select MONTHLY
	 from MRR_DATA
	union 
	 select date(MONTHLY, '+1 months')
	  from MRR_DATA
	  where MONTHLY = (select max(MONTHLY) from MRR_DATA)
	) MRR
	left outer join 
	    (select MONTHLY,
	 		NEW_MRR+EXPANSION_MRR-DOWNGRADE_MRR-CHURN_MRR as MRR
	    from MRR_DATA
	    ) MRR_BF
	on  MRR_BF.MONTHLY <= date(MRR.MONTHLY, '-1 months')
group by
    MRR.MONTHLY