title: How to manage an AJAX based 'like/dislike' feature?
body: <p>I'd like to add a like/dislike-upvote/downovote-type feature to each one of the posts in the forum script I'm writing (much like the one here in SO). I'm having two difficulties trying to figure out how it can be done:</p>
  
  <p>1) I can't figure out a db schema that'd do it efficiently. I could use a separate `likeordislike` table to make a relation between user and post (xyz likes post #123), or I can use a column of type \'text\' in the `posts` table listing out all the users who have liked (or disliked) the post. The latter of course means I'd have to parse the field for userIDs to make any use of it.</p>
  
  <p>2) Make sure the user doesn't get to like/dislike a post twice.</p>
  
  <p>It's probably trivial but I can only think of ways that make a lot of mysql calls on server side processes. Thanks.</p>