Using PHP to select and pair two users - php

Question

I'm trying to make an application that pairs two available users by selecting them randomly from a database and then making them unavailable (so they can't be selected again).
I was wondering how I could select them and then pair them?
I've got the following database structure.
USERS
| id | autoincrement, primary key
| user_id | user's ID
| connected | available, connecting, chatting
ROOMS
| id |
| room_name |
| room_id |
| user_id | first user connected
| user_id2 | second user connected
I'm not making rooms, I'm simply trying to pair users and send them to a room.

Answer 1

Do you mean join the records?
You could do something like:
select * from rooms as r
left outer join users as u on r.user_id=u.id
left outer join users as u2 on r.user_id2=u2.id
where r.id=123
123 = a room id.
EDIT:
Here is a way to update a Rooms record with two random Users
UPDATE rooms
SET
user_id=(SELECT id FROM users ORDER BY RAND() LIMIT 0,1),
user_id2=(SELECT id FROM users ORDER BY RAND() LIMIT 0,1),
where id=123
I have tested this and it seems to work. This will keep you from having duplicate users:
UPDATE rooms
SET
user_id=(SELECT u1.id FROM users as u1 ORDER BY RAND() LIMIT 0,1),
user_id2=(SELECT u2.id FROM users as u2 where user_id <> u2.id ORDER BY RAND() LIMIT 0,1)
where id=123

Answer 2

The SELECT could be something like this:
SELECT user_id
FROM `USERS`
WHERE connected = 'available'
ORDER BY RAND()
LIMIT 2;
You would need to parse the resultset and assign the to user_ids to variables such as
$user_id1
$user_id2
The first UPDATE would be something like this:
UPDATE `USERS`
SET connected = 'connecting'
WHERE user_id IN ($user_id1,$user_id2);
The INSERT would look something like this:
INSERT INTO `ROOMS` (room_name,room_id,user_id,user_id2)
VALUES ($room_name,$room_id,user_id,user_id2);
Finally the last UPDATE
UPDATE `USERS`
SET connected = 'connected'
WHERE user_id IN ($user_id1,$user_id2);
Although you are probably going to want to lock rows I have not grasped that part of database management yet. For you purposes you might want to look into it.

Answer 3

According to me you'll need three tables instead of two to implement your logic.
Consider my db schema
USERS
| id | autoincrement, primary key
| user_id | user's ID
| connected | available, connecting, chatting
ROOMS
| id |
| room_name |
USERCHAT
| id |
| user_id | user's ID
| room_id | room id
To get pair you can execute following query.
SELECT user_id
FROM USERS
WHERE id NOT IN (SELECT user_id FROM USERCHAT)
ORDER BY RAND()
LIMIT 2;
After selecting users you can simply insert them in ROOMS and USERCHAT tables. Using this schema you can also allow multiple users instead of two for chat.