SELECT gpstime, 
       MIN(gpstime) `mn`, 
       MAX(gpstime) `mx`, 
SEC_TO_TIME(SUM(TIME_TO_SEC(TIMEDIFF(max(gpstime), min(gpstime))))) AS  totalworktime
                         FROM   xydata a 
                         INNER JOIN fm4features f ON f.id = a.id
                         WHERE  objectid = 17 
                                AND clientid = 1
                                AND gpstime > '2010-05-11 00:00:00' 
                                AND gpstime < '2010-05-11 23:59:59' 
                                AND f.dataid = 1
                                AND f.VALUE = '1' 
                                AND gpstime IS NOT NULL                               
GROUP  BY Date_format(gpstime, '&#37;Y-%m-%d') 
ORDER  BY gpstime ASC