select DISTINCT a.* 
from advertisement a, company b, agent c,category_ad d 
where a.enabled=1 and a.company_id=b.id and b.agent_id=c.id and c.enabled=1 and a.category_ad_id=17
ORDER BY rand()
LIMIT 5

-- подготовка таблицы
drop temporary table if exists advertisement_temporary;
create temporary table advertisement_temporary (
   row_number int identity primary key,
   id int, ... <необходимые поля из ADVERTISEMENT>
select null row_number, a.id, ... <необходимые поля из ADVERTISEMENT>
   from advertisement a
   where a.category_ad_id=17 and a.enabled=1 
    and exists(
      select 1
      from company b 
      join agent c on c.id=b.agent_id and c.enabled=1
      -- cross join category_ad d 
      where b.id=a.company_id
    )
LIMIT 370 -- максимальное из требуемых (362, 295, 84, 370, 70)
;

-- получение требуемой выборки
select a.id, ... <необходимые поля из ADVERTISEMENT>
from advertisement_temporary a
where a.row_number in (362, 295, 84, 370, 70)
order by field(a.row_number, 362, 295, 84, 370, 70);

drop temporary table advertisement_temporary;