title: Group by the date part of a timestamp field
body: <p>I have <code>users</code> table. I would like to generate a report of user who joined for that day. 
  Problem is, my <code>DateJoined</code> field is a <code>timestamp</code> field,</p>
  
  <p><strong>As the query is following as:</strong></p>
  
  <pre><code>SELECT COUNT(UserID) AS TOT FROM users GROUP BY DateJoined
  </code></pre>
  
  <p>does not work, how do I get it to <code>GROUP BY</code> just the date part and not the time of <code>DateJoined</code> field?</p>