title: How to convert DATETIME to TIMESTAMP in mysql?
body: <p>I have DATETIME column in my table, with <code>2015-04-23 11:17:49</code> properties
  Trying to convert it to unix timestamp, acording to the mysql documentation I need just put the field into UNIX_TIMESTAMP() function and I'll get -> 1223423442 - timestamp but it's doesn't work, I've got only 0000-00-00 00:00:00
  Tried a lot of stuff:</p>
  
  <pre><code>// doesn't work
  UNIX_TIMESTAMP(CAST(`updated` AS CHAR(100))) AS updated_at,
  // doesn't work
  UNIX_TIMESTAMP(`updated`) AS updated_at,
  //doesn't work
  UNIX_TIMESTAMP(STR_TO_DATE(CAST(`created` AS CHAR(100)), \'%M %e %Y %h:%i%p\'))
                                  AS created_at'
  // doesn't work
  UNIX_TIMESTAMP(STR_TO_DATE(`created`, '%M %e %Y %h:%i%p'))
                                  AS created_at
  </code></pre>
  
  <p>Without `` doesn't work as well, am I missing something?</p>