public function get_fieldset_sql($sql, array $params=null) {
        $rs = $this->get_recordset_sql($sql, $params);
        if (!$rs->valid()) {
            $rs->close(); // Not going to iterate (but exit), close rs
            return false;
        }
        $result = array();
        foreach($rs as $value) {
            $result[] = reset($value);
        }
        $rs->close();
        return $result;
    }