title: $wpdb - what does it return on fail?
body: <p>I'm not sure whether this question is WordPress specific or is more related to mySQL.  I am trying to find out what would be returned if the transaction with the database fails.
  In the following scenario, I am updating a row.  If none of the values are changed false is returned.  If changes are made true is returned.  How can I tell if the transaction has failed?</p>
  
  <pre><code>$result = $wpdb-&gt;update($this-&gt;table_name, $dbfields, $where);
  if($result == false)//do fail - this is not really a fail!
  if($result == true)//do success
  </code></pre>
  
  <p>Any pointers appreciated.</p>