with t as (
    select monthly as YM, NEW_MRR+EXPANSION_MRR-DOWNGRADE_MRR-CHURN_MRR as m
    from MRR_DATA
)
select min(t.YM) as YM, 0 as MRR from t
union all
select date(max(t.YM), "+1 months"), sum(t.m) from t
union all
select t1.YM, sum(t2.m) as MRR
from t as t1
inner join t as t2 on t1.YM > t2.YM
group by t1.YM
order by t1.YM asc