public static function extractUpdateColumns($values)
    {
        $cls = get_called_class();
        $temp_columns = "";
        $escape = Driver::$escape_char;
        foreach ($values as $key => $value) {
            $temp_columns .= "$escape".self::$_mapping[$cls][$key]."$escape=?,";
        }
        return substr($temp_columns, 0, strlen($temp_columns)-1);
    }