Running a db query then running another query

[eluser]xwero[/eluser]

Code:

$query = $this->db->query("SELECT * FROM cacdp_menu_groups WHERE display_on_site = 'Y' ORDER BY list_order");
$rows = $query->result();

foreach($rows as $key => $row)
{
   $query = $this->db->query("SELECT * FROM cacdp_sub_navigation WHERE group_id = ? AND display_on_site = 'Y' ORDER BY list_order",array($row->group_id));
   $rows[$key]['sub_rows'] = $query_>result();
}