MySQL Query får de sista N raderna per grupp

I MySQL görs detta enklast med hjälp av variabler:

select t.*
from (select t.*,
             (@rn := if(@v = vehicle, @rn + 1,
                        if(@v := vehicle, 1, 1)
                       )
             ) as rn
      from table t cross join
           (select @v := -1, @rn := 0) params
      order by VehicleId, timestamp desc
     ) t
where rn <= 3;