Group mysql query by 15 min intervals

Try this , grouping of records of 15 minutes interval, you can change 15*60 to the interval in seconds you need

SELECT sec_to_time(time_to_sec(datefield)- time_to_sec(datefield)%(15*60)) as intervals from tablename
group by intervals

SELECT   FLOOR(UNIX_TIMESTAMP(timestamp)/(15 * 60)) AS timekey
FROM     table
GROUP BY timekey;