title: Sum time between dates in MySQL
body: <p>I have a MySQL table looking like this. It's basically a time sheet for tasks.</p>
  
  <pre><code>  id  |  task  |  user  |          start        |         stop          |  running
  ------+--------+--------+-----------------------+-----------------------+-----------
    1   |   12   |   2    |  2009-10-01 10:05:00  |  2009-10-01 14:23:00  |  0
    1   |   13   |   4    |  2009-10-05 08:58:00  |  2009-10-05 12:16:00  |  0
    1   |   14   |   3    |  2009-10-05 20:30:00  |  2009-10-05 22:00:00  |  0
  </code></pre>
  
  <p>I want to sum the time spent:</p>
  
  <p>1) Today
  2) Yesterday
  3) This week
  4) Last week
  5) This month
  6) Last month</p>
  
  <p>I don't need the queries for each of theese, but just the first one to get me started. I'm not that familiar with different date functions in MySQL, and I think it's difficult to read and navigate through their documentation..</p>