table a:
id, score

table ab:
a_id, b_id, b_type

table b:
id, name, type

name, count(group by name), average(score)

select name, count(*), average(score)
from a
joins ab
on a.id = ab.a_id
joins b
on b.id = ab.b_id
where type = 'sometype'
group by name
order by count(*) desc limit 10

select filtered_ab.b_id, count(1) as ct
from (
  select b_id
  from ab
  where b_type = 'sometype'
) as filtered_ab
group by filtered_ab.b_id
order by ct desc limit 1000

select name, b_id, ct
from b
join (
select filtered_ab.b_id, count(1) as ct
from (
  select b_id
  from ab
  where b_type = 'sometype'
) as filtered_ab
group by filtered_ab.b_id
order by ct desc limit 1000
) as b_with_counts
on b_with_counts.b_id = b.id