title: Processing columns inside SQL query?
body: <p>I have the following sample data:</p>
  
  <pre><code>id, user_id, action, date, item_id
  (5, 1, 'created', '2016-09-08, 1),
  (6, 1, 'sold', '2016-09-14, 1),
  (7, 2, 'created', '2016-09-08, 2),
  (8, 2, 'sold', '2016-09-30, 2),
  (9, 3, 'created', '2016-10-08, 3)
  </code></pre>
  
  <p>I'm trying to create a Query that returns the percentage of items sold within 1 week. The value of the <code>column: "action"</code> represents if the item has been put up for sale, or sold. How could this look?. Should I do this by using a subquery or?</p>
  
  <p>Expected result should be a single percentage (the number of items sold within 1 week, of the total number of items created). </p>