title: Use JOINS instead of subquery
body: <p>I have a simple query that uses a subquery:</p>
  
  <pre><code>SELECT pictures.*
  FROM pictures
  WHERE pictures.user_id IN
      (SELECT follows.following_id
       FROM follows
       WHERE follows.follower_id = 9)
  ORDER BY created_at DESC LIMIT 5;
  </code></pre>
  
  <p>I am wondering,
  a) How can I remove the sub query and use JOINS instead and b) will there be a performance benefit in using JOINS instead of sub query?</p>
  
  <p>(follows.following_id, follows.follower_id, pictures.user_id are all indexed)</p>
  
  <p>Thanks</p>