public function update()
    {
        $query = 'update '.$this->getTables($this->tables).' set ';
        //
        for ($i = 0; $i < Collection::count($this->sets); $i++) {
            if ($i < Collection::count($this->sets) - 1) {
                $query .= $this->sets[$i].',';
            } else {
                $query .= $this->sets[$i];
            }
        }
        //
        $query .= ' '.$this->where;
        //
        $this->reset();
        //
        return Database::exec($query);
    }