title: Comparing mysql timestamps
body: <p>I am trying to compare timestamps by finding out if particular timestamp field is greater than 15 days ago.</p>
  
  <p>So if I try this on my database, I get:</p>
  
  <pre><code>SELECT DATE_SUB(NOW(), INTERVAL 15 DAY) // 2012-04-08 11:00:54
  </code></pre>
  
  <p>The field concerned has a value: <code>2012-04-20 21:18:14</code>.</p>
  
  <p>So when I try:</p>
  
  <pre><code>SELECT * FROM (`payments`) WHERE `LastUpdated` &gt;= 'DATE_SUB(NOW(), INTERVAL 15 DAY)'
  </code></pre>
  
  <p>I get no rows returned? Am I comparing dates incorrectly?</p>