public function unique($name, array $colmuns)
    {
        if (is_array($colmuns)) {
            $query = "CONSTRAINT $name UNIQUE (";
            //
            for ($i = 0; $i < Collection::count($colmuns); $i++) {
                if ($i == Collection::count($colmuns) - 1) {
                    $query .= $colmuns[$i];
                } else {
                    $query .= $colmuns[$i].',';
                }
            }
            $query .= ')';
            //
            self::$colmuns[] = $query;
        }
        //
        return $this;
    }