title: window function-choose the most recent row
body: <p>I need to select the most recent row based on the Creation Date.
  Here is my table:</p>
  
  <pre><code>REF X      REF Y            EMLOYEE CREATION DATE
  2879074 DLP/2015.01551-B.01 Didier  3/5/2015
  2879074 DLP/2015.00841-A.01 Didier  2/5/2015
  2879074 DLP/2015.00146-A.01 jacques 1/8/2015
  2879074 DLP/2014.07840-A.02         1/6/2015
  2879074 DLP/2014.05967-B.03 diet    6/21/2016
  2879074 DLP/2014.05967-B.03 ext     6/21/2016
  2879074 DLP/2014.05967-B.02 David   10/21/2015
  2879074 DLP/2014.05967-B.02 ieva    10/21/2015
  2879074 DLP/2014.05967-B.02 laetitia10/21/2015
  2879074 DLP/2014.05967-B.02 PLN 10/21/2015
  2879074 DLP/2014.05967-B.01 David   4/14/2015
  2879074 DLP/2014.05967-B.01 ieva    4/14/2015
  2879074 DLP/2014.05967-B.01 laetitia4/14/2015
  2879074 DLP/2014.05967-B.01 PLN    4/14/2015
  2733407 DLP/2014.00138-B.03 Andy    9/6/2016
  2733407 DLP/2014.00138-B.03 Nell    9/6/2016
  2733407 DLP/2014.00138-B.03 stephane9/6/2016
  2733407 DLP/2014.00138-B.02 Andy    2/17/2016
  2733407 DLP/2014.00138-B.02 Nell    2/17/2016
  2733407 DLP/2014.00138-B.02 nicola  2/17/2016
  2733407 DLP/2014.00138-B.02 diet    2/17/2016
  2733407 DLP/2014.00138-B.01 herve   3/10/2015
  2733407 DLP/2014.00138-B.01 nicola  3/10/2015
  </code></pre>
  
  <p>The output should be:</p>
  
  <pre><code>Ref x   Ref y   employee           Creation Date
  2879074 DLP/2014.05967-B.03 diet    6/21/2016
  2879074 DLP/2014.05967-B.03 ext     6/21/2016
  2733407 DLP/2014.00138-B.03 Andy    9/6/2016
  2733407 DLP/2014.00138-B.03 Nell    9/6/2016
  2733407 DLP/2014.00138-B.03 stephane9/6/2016
  </code></pre>
  
  <p>I'm guessing I have to use window function, but I have trouble listing the correct REF Y. Any help would be appreciated
  Many thanks</p>