title: Update last modified date column
body: <p>I have a table like this:</p>
  
  <pre><code>id  name    modified
  11  John    2016-07-12 15:49:45
  22  Abraham 2016-07-12 15:52:03
  </code></pre>
  
  <p>I need to update the 'modified' column which tracks the last modified date for a row.  I have done this using a trigger, but have read that triggers eat up performance. Is there a way to do this using constraints? </p>