title: Update SQL Query for varchar(max) column
body: <p>How to update a <code>varchar(max)</code> column to an empty string from null value?</p>
  
  <p>Here is the pseudo code:</p>
  
  <pre><code>UPDATE tablename 
  SET all varchar(max) columns ='' 
  WHERE varchar(max) == NULL
  </code></pre>
  
  <p>Need to create something like this, any help will be appreaciated!</p>