Witam, w pgsql wygląda to właśnie tak:
select a.name, b.ownerid,count (b.id) as ilosc_kompow from networks a
left join nodes b on b.ipaddr >= a.address and b.ipaddr <= broadcast(a.address, inet_aton(a.mask))
group by a.name, b.ownerid
having count (b.id) >=2
Ostatni parametr (having count (b.id) >=2) określa ile kompów ma mieć jeden owner
Pozdrawiam Miłosz