public function exists($oxid = null)
    {
        if (!$oxid) {
            $oxid = $this->getId();
        }
        if (!$oxid) {
            return false;
        }

        $viewName = $this->getCoreTableName();
        $database = \OxidEsales\Eshop\Core\DatabaseProvider::getDb(\OxidEsales\Eshop\Core\DatabaseProvider::FETCH_MODE_ASSOC);
        $query = "select {$this->_sExistKey} from {$viewName} where {$this->_sExistKey} = " . $database->quote($oxid);

        return ( bool ) $database->getOne($query);
    }