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

Or slotting neatly between GL's two answers (performancewise anyway)...

SELECT x.*, AVG(y.speed) avg
  FROM my_table x
  JOIN my_table y
    ON y.id <= x.id
 GROUP 
    BY x.id;