Question

I have a database with users and games. 1 game can have multiple users so I made a linking table called users_games. The crux is that a game can always only have 2 players since it is a board game. I know which player I am, i have my user_id and my email, but I would like to gain a result that gives me a list of all games I am in WITH the user_id and email of the other fellow. So a query that looks to all games I am in and give the other row, with the name of the player.

My tables:

games

id (int)
board (varchar) representation of the board

users

id (int)
email (varchar)
password (varchar MD5)

users_games

id (int)
user_id (int)
game_id (int)

For clarification this query

SELECT * 
        FROM `tic_users_games` AS ug 
        LEFT JOIN tic_users AS u
        ON ug.user_id = u.id
        RIGHT JOIN tic_games AS g
        ON ug.game_id = g.id

And result

id  user_id     game_id     id  email   password    id  board   created     updated 

1   1   1   1   [e-mail]    d56b699830e77ba53855679cb1d252da    1   0|0|0|0|0|0|0|0|0   2012-04-02 16:56:06     2012-04-02 16:56:06
2   2   1   2   [e-mail]  d56b699830e77ba53855679cb1d252da    1   0|0|0|0|0|0|0|0|0   2012-04-02 16:56:06     2012-04-02 16:56:06
3   3   2   2   [e-mail]  d56b699830e77ba53855679cb1d252da    2   0|0|0|0|0|0|0|0|0   2012-04-02 16:56:06     2012-04-02 16:56:06
4   1   2   1   [e-mail]    d56b699830e77ba53855679cb1d252da    2   0|0|0|0|0|0|0|0|0   2012-04-02 16:56:06     2012-04-02 16:56:06

See: In the above case I just want 2 rows: game_id 1 and 2, with FOE1@… and FOE2@…

Thanks

Answer 1

This should do it for you. The syntax might not be exact for mysql but you should get there. Basically get all users that have games in the user_games table with the same game_ID as the games I am in:

SELECT
    User_Games.Game_ID,
    Users.ID,
    Users.Email
FROM
    Users 
    LEFT JOIN User_Games ON Users.ID = User_Games.User_Id
WHERE
    Users.User_ID <> @yourUserID
AND EXISTS
    (SELECT
        NULL
    FROM
        User_Games AS MyUserGames
    WHERE
        User_Games.Game_ID = MyUserGames.Game_ID
    AND MyUserGames.User_ID = @yourUserID)