title: Azure Data Factory Exist Transformation
body: <p>Is there a way that after comparing two tables and then use the Case function?</p>
  <p>I am trying to have a new column base on Exists transformation. In sql I do it like this:</p>
  <pre><code>(isnull (select 'YES' from sales where salesperson = t1.salesperson group by salesperson), 'NO')) AS registeredSales
  
  T1 is personal.
  </code></pre>
  <p>Or should I include the table into the stream of the joins and then use the case() function to compare the two columns?</p>
  <p>If there's another way to work around to compare these two streams, I would be pleased to hear.</p>
  <p>Thanks.</p>