title: select top n rows of each subquery
body: <p>I have this structure:</p>
  
  <pre><code>posts:
      id, content, created_at
  
  comments:
      id, post_id, content, created_at
  </code></pre>
  
  <p>now I would like to select 10 posts ordered by created_at desc,
  limit to only 10 posts.
  AND now the problem,
  I would like to get each post last 5 comments.</p>
  
  <p>I have no problem doing this seperatly, but it will produce me 11 queries....
  one fore getting the posts,
  and another 10 queries for each posts and selecting it's comments.</p>
  
  <p>any ideas on how to reduce this queries?</p>