public function ids($select, $values = array())
    {
        $ids = array();
        if ($stmt = $this->query($select, $values, 'row')) {
            while ($row = $this->fetch($stmt)) {
                $ids[] = (int) array_shift($row);
            }
            $this->close($stmt);
        }

        return (!empty($ids)) ? $ids : false;
    }