Question

I have a query that retrieves the users that are online, and a users friends. Now I want to know the best way to combine the two so I can get the results of the users friends that are online.

Friends query:

 SELECT 
       CASE WHEN userID=$session 
       THEN userID2 
       ELSE userID 
       END AS friendID 
 FROM friends 
 WHERE userID=$id OR userID2=$session
 LIMIT 18

users online:

SELECT * 
FROM usersActivity 
WHERE setActivity!=3 
AND userID!=$session

usersActivity.userID needs to match friendID

Answer 1

Query should be:

SELECT users.name
FROM usersActivity
INNER JOIN friends ON
    (usersActivity.userID = usersActivity.userID AND usersActivity.userID2 = $session) OR
    (usersActivity.userID2 = usersActivity.userID AND usersActivity.userID = $session)
INNER JOIN users ON
    (usersActivity.userID = users.userID) OR
    (usersActivity.userID2 = users.userID)
WHERE usersActivity.setActivity!=3 
    AND usersActivity.userID!=$session
    AND users.userID != $session
GROUP BY users.id

You may use COUNT(user.id) if you want only count of users. Or select all names (store them for later use in listing) and use only mysql_num_rows() for getting actual number of friends online