running average in mysql

Question

I have the table like below

id   timestamp  speed
1    11:00:01   100
2    11:05:01   110
3    11:10:01   90
4    11:15 :01  80

I need to calcu

Answer 1

Does MySQL support windowing functions?

select
  id, timestamp, speed,
  avg (speed) over (order by timestamp) as average
from tbl

If it doesn't this might work, although I doubt it's efficient:

select
  min (t1.id) as id, t1.timestamp, min (t1.speed) as speed,
  avg (t2.speed)
from
  tbl t1
  join tbl t2 on
    t2.id <= t1.id
group by
  t1.timestamp
order by
  t1.timestamp