title: Does an index < or > MySQL queries?
body: <p>If I have a query like, </p>
  
  <pre><code>DELETE FROM table WHERE datetime_field &lt; '2008-01-01 00:00:00'
  </code></pre>
  
  <p>does having the <code>datetime_field</code> column indexed help?  i.e. is the index only useful when using equality (or inequality) testing, or is it useful when doing an ordered comparison as well?</p>
  
  <blockquote>
    <p>(Suggestions for better executing this query, without recreating the table, would also be ok!)</p>
  </blockquote>