DELETe FROM `80dage_garmin_track` t1 WHERe EXISTS (SELECt 1 from `80dage_garmin_track` t2 WHERe t1.Length = t2.LengthAND t1.Time = t2.TimeAND t1.idgarmin_track > t2.idgarmin_track)

DELETe FROM `80dage_garmin_track` t1 WHERe EXISTS (SELECt 1 from `80dage_garmin_track` t2 WHERe t1.Length = t2.LengthAND t1.Time = t2.TimeAND t1.idgarmin_track > t2.idgarmin_track)