with base(YM,MRR) as (
select 
    min(MONTHLY)
    ,0
from
    MRR_DATA
union all
select
    date(MONTHLY,"+1 month")
    , NEW_MRR+EXPANSION_MRR-DOWNGRADE_MRR-CHURN_MRR
from
    MRR_DATA
)
select
    YM
    ,sum(MRR) over(order by YM ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) as MRR
from
    base
order by
    YM