PostgreSQL | PGExercises.com | Months to repay

-- https://pgexercises.com/questions/aggregates/payback.html
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'''
We spent initialoutlay per facility
Every month we spend monthlymaintenance per facility
Every month we receive revenue per facility
Difference between revenue and monthly maintenance is what counts against initialoutlay per facility
'''
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with t1 as (select
    name,
    initialoutlay,
    monthlymaintenance,
    sum(slots * (case when memid=0 then guestcost else membercost end))/3 as monthlyrevenue
from cd.facilities f
join cd.bookings b
on f.facid = b.facid
group by 1, 2, 3)

select  name,
        initialoutlay/(monthlyrevenue-monthlymaintenance) as months
from t1
order by 1 asc