title: How to populate empty columns with unique values in SQL Server?
body: <p>I have a table which have a row containing user emails and I want to add a constraint to make this row unique. The problem is that there are some (around 200) columns with empty values.</p>
  
  <p>I need to generate dummy values and insert them to the empty columns.</p>
  
  <p>How can I do it?</p>
  
  <p>Thanks</p>