title: MySQL trigger: Update when reaching a certain datetime
body: <p>I want to create a MySQL trigger that updates a table everytime one of the datetime rows in a different table reaches a datetime lower than now.</p>
  
  <p><strong>How would I accomplish this? Is that even possible?</strong></p>
  
  <p>To illustrate:</p>
  
  <pre><code>table_1                           table_2      
  --------   -------------------    --------   -
  id         1                      id         1
  datetime   2011-05-10 11:11:11    counter    1
  </code></pre>
  
  <p>So, when time passes and <code>NOW()</code> becomes <code>2011-05-10 11:11:12</code>, then I want to have the counter upped by 1.</p>