title: Select Only one row per ID and Date
body: <p>I need to do something in SQL and I'm currently confused!</p>
  
  <p>So I have something like this:</p>
  
  <pre><code>idEvent   idService   dateCreated
  -------   ---------   -----------
  1         1           2012-01-01
  2         1           2012-02-02
  3         2           2012-01-01
  4         2           2012-02-02
  </code></pre>
  
  <p>The <code>idEvent</code> is auto-incrementing.</p>
  
  <p>What I need to get is the biggest row (ordered by <code>dateCreated DESC</code>) for each <code>idService</code>.</p>
  
  <p>So I'd need to get this as a result :</p>
  
  <pre><code>idEvent
  -------
  2
  4
  </code></pre>