Question

Consider a site where a user can rate games. The ratings available are: None, Liked, or Disliked. The code will keep track of the ratings just fine. The current problem is a user can rate a game and just keep re-rating it.

How would a SQL table look if I wanted to store a user’s rating for a certain game? Duplicate ratings for each user/game shouldn’t be allowed.

Answer 1

You can use the following tables:

user:
  id
  name
  ...

game:
  id
  name
  ...

user_rating:
  user_id
  game_id
  rating

where user_id and game_id refer to user and game. They both form the PRIMARY KEY, so the model does not support a user rating more than once.

rating contains -1, 0, or +1 and can be summed to get the score of a game.