subquery aggregation
select name, revenue from (
select facs.name, sum(case
when memid = 0 then slots * facs.guestcost
else slots * membercost
end) as revenue
from cd.bookings bks
inner join cd.facilities facs
on bks.facid = facs.facid
group by facs.name
) as agg where revenue < 1000
order by revenue;