Question

I got a users table and movies table, each user could watch more then one movie.

Now I want to find all the users who watched particular movie,
How should my tables looks like in MySql?

Answer 1

To do this, you need 3 tables. The first two are users and movies, they would, in a very basic form, look like this:

user
  id
  name

movie
  id
  title

Since many users can watch many movies and the same movie can be watched by multiple users, there’s a many-to-many relationship there. To define such a relationship in MySQL, you need a third table called a join table, that knows which user watched which movie (I called this user_movies but you might want to go with a different name):

user_movies
  user_id
  movie_id

To know who watched a movie called Spaceballs, you need a query like this:

SELECT u.name FROM user u 
  JOIN user_movies um ON um.user_id = u.id 
  JOIN movie m ON um.movie_id = m.id
    WHERE m.title = 'Spaceballs'