title: Oracle SQL -- look for new users that were not shown in last week
body: <p>I generate report in XL sheet every week, using a DB which tracks the users of a website. I have to find the list of my web application users who didn't show up in previous report, which was generated last week. </p>
  
  <p>DB Structure with data(table has two columns <strong>WebAppUserName</strong> and <strong>URL</strong>):     </p>
  
  <pre><code>WebAppUserName           URL  
  Tom                       google.com
  </code></pre>
  
  <p>first week Data in DB:</p>
  
  <pre><code>  Tom                      google.com
    Jim                      google.com/test
    Ken                      google.com/test
  </code></pre>
  
  <p>Second week (last week)Data in DB:</p>
  
  <pre><code>  Tom                      google.com
    Jim                      google.com/test
  </code></pre>
  
  <p>This week(Third week) Data in DB:</p>
  
  <pre><code> Tom                      google.com
   Jim                      google.com/test
   Ken                    google.com/test
   Ron                    google.com/test
  </code></pre>
  
  <p>Since Ken and Ron didn't appeared in the last week Data and they both appeared in this week data, >I need to retrieve only Ken and Ron's information and not the other users. How to write a Query for >this.</p>