Q:

How to perform join in parse database

I have a requirement which is as follows. 
User will get login and select certain number of sport Clubs around them. After that data will be stored in a separate parse class. Now after storing this sport clubs i want to show people who interested in same sport clubs. 
I have created three classes 
1)User = All the user information 
2)SportClubs = All the sport club information 
3)UserSportClub = objectid, UserID :Pointer,sportclubs : Pointer
Now i want keep network calls minimum and fetch all other users who 
 are interested in my selected spotclubs.
let query = PFQuery(className: "UsersSelectedSportClubs")
    query.whereKey("userID", equalTo: PFUser.currentUser()!)
    // execute the query
    query.findObjectsInBackgroundWithBlock {
        (objects: [AnyObject]?, error: NSError?) -> Void in
        if let objects = objects {
            for object in objects {
                /* 1) We get the SportclubID */
                let sportclub = object.objectForKey("sportclubID") as? PFObject
                /* 2) Fetch all users from who like this sportclub*/
                println(sportclub)
                    let usersQuery = PFQuery(className: "UsersSelectedHotspots")
                    //usersQuery.whereKey("sportclubID", equalTo: sportclub!)
                    usersQuery.whereKey("userID", notEqualTo: PFUser.currentUser()!)
                /*Getting all users who like this sportclubs.*/
                query.findObjectsInBackgroundWithBlock {
                    (objects: [AnyObject]?, error: NSError?) ->
                    Void in
                    if let objects = objects {
                        for object in objects {
                           let otherUse = object.objectForKey("userID") as? PFUser
                            println(otherUse)
                        }
                    }
                }
            }
        }
    }

A:

Parse is NoSQL database so in it there are no JOIN methods. U could make another table with needed information (example: user | sportsclub | isInterested). Or u could make subquery like
ParseQuery<ParseObject> query = ParseQuery.getQuery("User");
query.whereContains("favouriteSportsClub")

