туплю с простым sql запросом на группировку

select bugs.* from bugs
  inner join (select project_id, max(created_at) as created_at from bugs group by project_id) last_bugs 
    ON last_bugs.project_id=bugs.project_id and last_bugs.created_at=bugs.created_at

select * from test.bugs as b1
	where b1.created_at = (select MAX(b2.created_at) from test.bugs as b2 where b1.project_id = b2.project_id);

 select *
 from   project p join
        ( select *
          from   ( select *
                   from   bugs bb
                   where  bb=p.id
                   order by bb.created_at
                 ) xxx
          where rownum=1
        ) yyy on p.id=yyy.project_id