protected function _renderOrder($sql)
    {
        if ($this->_parts[self::ORDER]) {
            $order = array();
            foreach ($this->_parts[self::ORDER] as $term) {
                if (is_array($term)) {
                    if(is_numeric($term[0]) && strval(intval($term[0])) == $term[0]) {
                        $order[] = (int)trim($term[0]) . ' ' . $term[1];
                    } else {
                        $order[] = $this->_adapter->quoteIdentifier($term[0], true) . ' ' . $term[1];
                    }
                } else if (is_numeric($term) && strval(intval($term)) == $term) {
                    $order[] = (int)trim($term);
                } else {
                    $order[] = $this->_adapter->quoteIdentifier($term, true);
                }
            }
            $sql .= ' ' . self::SQL_ORDER_BY . ' ' . implode(', ', $order);
        }

        return $sql;
    }