title: Mysql - when trying to UPDATE a timestamp column. It fails to update
body: <p>I think I may have encountered a bug in mysql, or is it just me doing it wrong.</p>
  
  <p>I've been using the same specific queries for the last four months and just today it stopped working somehow. I can't see the problem. </p>
  
  <p>I'm executing these queries in the mysql console it works great, and the field is being updated. but when these queries are being executed by PHP it fails. </p>
  
  <p>After insertion of a record into a table(with two timestamp fields), I'm trying to update a specific timestamp column.</p>
  
  <p>But unfortunately it fails to update the column.</p>
  
  <p>The query goes well(no errors), but still the value in the timestamp column stays the same. That's weird, cause when I'm leaving the initial column value as NULL, the update query succeed.</p>
  
  <p>Columns : </p>
  
  <pre><code>START_DATETIME, END_DATETIME - are "timestamp" type.
  </code></pre>
  
  <p>Insert:</p>
  
  <pre><code>INSERT INTO TABLE1(START_DATETIME, END_DATETIME, RESPONSE) 
  VALUES(NOW(), NOW(), 'STARTED')
  </code></pre>
  
  <p>Insert is done successfully. id is 123</p>
  
  <p>The update query is normal like any other query:</p>
  
  <pre><code>UPDATE TABLE1 
  SET END_DATETIME = NOW(), RESPONSE='ENDED'
  WHERE ID = 123
  </code></pre>
  
  <p>Update fails, <code>END_DATETIME</code> doesn't get the <code>NOW()</code> value.</p>
  
  <p>Can be reproduced with this:</p>
  
  <pre><code>CREATE TABLE TABLE1 
  (
      id int auto_increment, 
      start_datetime timestamp, 
      end_datetime timestamp, 
      response varchar(100), 
  
      primary key(id)
  );
  </code></pre>