protected function build()
    {
        $sql = "SELECT\n\t"
            . $this->columns . "\n"
            . $this->from . "\n"
            . ($this->join    ? $this->join           : null)
            . ($this->where   ? $this->where . "\n"   : null)
            . ($this->groupby ? $this->groupby . "\n" : null)
            . ($this->orderby ? $this->orderby . "\n" : null)
            . ($this->limit   ? $this->limit . "\n"   : null)
            . ($this->offset  ? $this->offset . "\n"  : null)
            . ";";

        return $sql;
    }