title: use JSON column or a separate table to store a list of things of the same type in mysql
body: <p>A User can have many Posts, I'm wondering whether I should store the ids of the Posts in a JSON column in the User table or I should create a separate table with composite primary key(user_id, post_id)?</p>
  
  <p>If there are 10 million user, and each user has 100 posts, the separate table method will have 1 billion records, this doesn't seem very good for scaling or efficient.</p>
  
  <p>Which method would be the better choice in this case? Does one have better performance than the other? </p>