Laravel Pivot Table, Get Room belonging to users - laravel

Question

The structure of my pivot table is
room_id - user_id
I have 2 users that exist in the same room.
How can I get the rooms they both have in common?
It would be nice to create a static class to have something like this.
Room::commonToUsers([1, 5]);
Potentially I could check more users so the logic must not restrict to a certain number of users.
Room::commonToUsers([1, 5, 6, 33, ...]);

Answer 1

I created a Laravel project and make users, 'rooms', 'room_users' tables and their models
and defined a static function in RoomUser Model as below :
public static function commonToUsers($ids)
{
$sql = 'SELECT room_id FROM room_users WHERE user_id IN (' . implode(',', $ids) . ') GROUP BY room_id HAVING COUNT(*) = ' . count($ids);
$roomsIds = DB::select($sql);
$roomsIds = array_map(function ($item){
return $item->room_id;
}, $roomsIds);
return Room::whereIn('id', $roomsIds)->get();
}
in this method, I use self join that the table is joined with itself, A and B are different table aliases for the same table, then I applied the where condition between these two tables (A and B) and work for me.
I hope be useful.

Answer 2

I don't know the names of your relations, but I guess you can do like this :
$usersIds = [1, 5];
$rooms = Room::whereHas('users', function($query) use ($usersIds) {
foreach ($usersIds as $userId) {
$query->where('users.id', $userId);
}
})->get();
It should work. whereHas allows you to query your relation. If you need to have a static method, you can add a method in your model.

Answer 3

There might be a more efficient way but laravel collection does have an intersect method. You could create a static function that retrieves and loop through each object and only retain all intersecting rooms. something like this
public static function commonToUsers($userArr){
$users = User::whereIn('id',$userArr)->get();
$rooms = null;
foreach($users as $user){
if($rooms === null){
$rooms = $user->rooms;
}else{
$rooms = $rooms->intersect($user->rooms);
}
}
return $rooms;
}
This code is untested but it should work.

Answer 4

Room has many users, user has many rooms, so you can find the room which have those two users.
If your pivot table's name is room_users, then you can easily get the common room like this:
public static function commonToUsers($user_ids) {
$room = new Room();
foreach($user_ids as $user_id) {
$room->whereHas('users', function($query) use ($user_id) {
$query->where('room_users.user_id', $user_id);
});
}
return $room->get();
}
This code will convert to raw sql:
select *
from `rooms`
where exists (
select * from `rooms` inner join `room_users` on `rooms`.`id` = `room_users`.`room_id` where `rooms`.`id` = `room_users`.`room_id` and `room_users`.`user_id` = 1
)
and exists
(
select * from `rooms` inner join `room_users` on `rooms`.`id` = `room_users`.`room_id` where `rooms`.`id` = `room_users`.`room_id` and `room_users`.`user_id` = 5
)