with W as (
select
	C.MONTHLY as cur,
	P.MONTHLY as past,
	(case when C.NEW_MRR is null then 0 else C.NEW_MRR + C.EXPANSION_MRR - C.DOWNGRADE_MRR - C.CHURN_MRR end) as MRR_C,
	(case when P.NEW_MRR is null then 0 else P.NEW_MRR + P.EXPANSION_MRR - P.DOWNGRADE_MRR - P.CHURN_MRR end) as MRR
from
	MRR_DATA C
left outer join
	MRR_DATA P
on
	datetime(C.MONTHLY) = datetime(P.MONTHLY, '+1 months')
)

select 
    W1.cur as YM,
    sum(W2.MRR) as MRR
from 
    W W1
inner join
    W W2
on
    W1.cur >= W2.cur
group by
    W1.cur
order by W1.cur asc