title: How to check for a zer0 timestamp in MySql?
body: <p>I have a MySql table with some fields which are of type <code>TIMESTAMP</code>.</p>
  
  <p>I want to detect those which are "invalid" (have never had data inserted and there is no default).</p>
  
  <p>Is there some MySql constant I can use ? e.g <code>SELECT .. WHERE timestamp_column=INVALID_DATE_TIME</code></p>
  
  <p>Or should I just compare with "0000-00-00 00:00:00 "?</p>