Maybe I was not clear as I should be but here is an example in Firebird:

select something,anotherthing,(select sum(thirdthing) from second b where b.something = a.something) total from a where

(select sum(thirdthing) from second b where b.something = a.something) > 10

 

tray sentence:

select a.someting, a.anotherthing, b.total

from first a inner join (

select someting,sum(thirdhing) as total

from second group by someting ) b on a.someting=b.someting

where b.total>10