title: Check if a column's value is null in SQL Server
body: <p>Can't believe I am stuck with this but how can I check that value I am returning is null in select statement</p>
  
  <pre><code>IF EXISTS(SELECT TU.Tagged FROM TopicUser TU 
            WHERE TU.TopicId = @TopicId and TU.UserId = @UserId)
  BEGIN
      --do stuff
  END
  </code></pre>
  
  <p>The value of <code>TU.Tagged</code> is <code>NULL</code> but yet it does go into the condition. In mind it does not exist. </p>