start_serialnumber)->serialnumber; } public function getEndNumAttribute() { return IntervalEquipment::find($this->end_serialnumber)->serialnumber; } public function start() { return $this->belongsTo(IntervalEquipment::class, 'start_serialnumber', 'serialnumber'); } public function end() { return $this->belongsTo(IntervalEquipment::class, 'end_serialnumber', 'serialnumber'); } }