Codeigniter - select where id not in (another query result)

Question

I'm working into a hotel booking system, currently I'm trying to select available rooms (not reserved).

Rooms DB Structure:
ID
ROOM NAME
CAPACITY

HOTEL RESERVATIONS DB STRUCTURE:
ID
CHECK_IN
CHECK_OUT
ROOMS
...

This is my current code:

function searchFreeRooms($data){
  $check_in = $data['fields']['check_in'];
  $check_out = $data['fields']['check_out'];
  $this->db->select("*");
  $this->db->from('core_hotel_rooms');
  $this->db->where("id NOT IN (select rooms,total_guests from res_hotel where check_in <= '$check_in' AND check_out >= '$check_in' OR check_in <= '$check_out' AND check_out >= '$check_out' OR check_in >= '$check_in' AND check_out <= '$check_out' ) ");
  $query = $this->db->get();
  return $query->result();
 }

A user can book many rooms in one time, and reserved room id's are stored in column "ROOMS" seperated with commas ex: 2, 3, 5

In my front, room that exist in this column should not be displayed but I'm having trouble because only first id(room) before comma is selected, example: 2,3,5 > only 2 is selected and 3,5 still are displayed in my front.

Problem is here: $this->db->where("id NOT IN (select rooms,total_guests from res_hotel where check_in <= '$check_in' AND check_out >= '$check_in' OR check_in <= '$check_out' AND check_out >= '$check_out' OR check_in >= '$check_in' AND check_out <= '$check_out' ) ");

I tried this: $this->db->where("id NOT IN (1, 2) "); and it works perfectly but not upper method with second query.

Sorry for my english...

Many thanks to all those who can help!

Answer 1

Finally with all your help I've fixed my problem!

Working code:

function searchFreeRooms($data){
  $check_in = $data['fields']['check_in'];
  $check_out = $data['fields']['check_out'];
  $query1 = $this->db->query("select rooms from res_hotel where (check_in <= '$check_in' AND check_out >= '$check_in') OR (check_in <= '$check_out' AND check_out >= '$check_out') OR (check_in >= '$check_in' AND check_out <= '$check_out' )");
  $query1_result = $query1->result();
  $room_id= array();
  foreach($query1_result as $row){
     $room_id[] = $row->rooms;
   }
  $room = implode(",",$room_id);
  $ids = explode(",", $room);
  $this->db->select("*");
  $this->db->from('core_hotel_rooms');
  $this->db->where_not_in('id', $ids);
  $query = $this->db->get();
  return $query->result();
 }

Thanks a lot!