protected function _addRelation($select)
    {
        // now add a left join with the round table so we have all tokens, also the ones without rounds
        if (!is_null($this->_gemsData['gto_id_relation'])) {
            $select->forWhere('gto_id_relation = ?', $this->_gemsData['gto_id_relation']);
        } else {
            $select->forWhere('gto_id_relation IS NULL');
        }
    }