SELECT sql_calc_found_rows                                          gstime, 
       MAX(stoptime)                                                AS mx, 
       MIN(starttime)                                               AS mn, 
       Sec_to_time(SUM(Time_to_sec(Timediff(stoptime, starttime)))) AS totalworktime 
FROM   (SELECT gstime, 
               gstime                                               AS stoptime, 
               Coalesce((SELECT MAX(b.gstime) 
                         FROM   xydata b 
                         WHERE  objectid = '17' 
                                AND clientid = '1' 
                                AND gstime > '2010-04-20 08:22:27' 
                                AND gstime < '2010-04-26 10:22:27' 
                                AND b.objectid = a.objectid 
                                AND b.gstime < a.gstime), gstime) AS starttime 
        FROM   xydata a 
               INNER JOIN fm4features f 
                 ON f.id = a.id 
        WHERE  objectid = '17' 
               AND clientid = '1' 
               AND gstime > '2010-04-20 08:22:27' 
               AND gstime < '2010-04-26 10:22:27' 
               AND f.dataid = '1' 
               AND f.VALUE = '1') derived 
GROUP  BY Date_format(gstime, '%Y-%m-%d') 
ORDER  BY gstime ASC

1	PRIMARY	<derived2>	ALL					2749	100	Using temporary; Using filesort
2	DERIVED	a	range	PRIMARY,id_objid	id_objid	16		33392	100	Using where; Using index
2	DERIVED	f	ref	ID	ID	4	navl.a.ID	3	100	Using where
3	DEPENDENT SUBQUERY	b	range	id_objid	id_objid	16		33392	100	Using where; Using index

xydata	CREATE TABLE `xydata` (
  `ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `Longi` varchar(255) DEFAULT NULL,
  `Lat` varchar(255) DEFAULT NULL,
  `Altitude` int(11) NOT NULL,
  `Angle` int(11) NOT NULL,
  `Satellite` int(11) NOT NULL,
  `Speed` int(11) NOT NULL,
  `ObjectId` int(10) unsigned NOT NULL,
  `ClientId` int(10) unsigned NOT NULL,
  `GpsTime` datetime NOT NULL,
  `Location` varchar(255) DEFAULT NULL,
  `City` varchar(255) DEFAULT NULL,
  `State` varchar(255) DEFAULT NULL,
  `Distance` varchar(100) DEFAULT NULL,
  `Times` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`ID`),
  KEY `id_objid` (`ObjectId`,`ClientId`,`GpsTime`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=70354 DEFAULT CHARSET=latin1 ROW_FORMAT=COMPRESSED

fm4features	CREATE TABLE `fm4features` (
  `ID` int(10) unsigned NOT NULL DEFAULT '0',
  `DataId` int(11) NOT NULL,
  `Value` varchar(20) NOT NULL,
  KEY `ID` (`ID`),
  CONSTRAINT `new_xydata_id` FOREIGN KEY (`ID`) REFERENCES `xydata` (`ID`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1 ROW_FORMAT=COMPRESSED