title: how to use where condition in mongodb
body: <p>I have a collection of mongodb, which contains "MoviesID, UserID, Rating", so this is to describe the how the users rate different movies, and a user can rate different movies, and certainly a movie can be rated by different users. Now I want to find all the users who rate similar movies with target user(For example : user 5).  Rating similar movies means that they rate at least same movie, or more. So how should I find all the users who rate similar movie with user 5? I just start learning mongodb.  Thanks!</p>