select f.id, f.sname, a.* from fin f
left join (
  select i_time, fin, l_price, best_buy, deal_max, deal_min from inf_ac 
  where fin in (
    select fin from inf_ac group by fin
  ) and i_time in (
    select max(i_time) from inf_ac group by fin
  )
) a on f.id = a.fin;