title: Dax Measure : COUNT Unique Articles Week over Week
body: <p>I have a huge transactional table that shows me the weekly sales.
  The columns are</p>
  <ul>
  <li>Year-Week</li>
  <li>Product</li>
  <li>Value</li>
  </ul>
  <p>Now I would like to determine, how many new products were sold this week compared to last week.
  DISTINCTCOUNT will not work here, right? Do I need CALCULATEDTABLE?
  How would you do that?</p>