title: Storing arrays in database : JSON vs. serialized array
body: <p>With ruby-on-rails, I want to store an array of 3 elements: the last 3 comments of a post. I know I could join the Comment table to the Post one, but I would avoid to do this heavy request for scaling purposes.</p>
  
  <p>So I was wondering what was the best way to store those 3 elements, as I would like to update them easily every time a new comment is made: remove the last comment and add the new one.</p>
  
  <p>What is the correct way to do this ? Store it in a serialized array or in a JSON object ?</p>