title: SQL case 0 then NULL
body: <p>I want to get <code>NULL</code> when the number in my table is 0. How can I achieve this using SQL? I tried</p>
  <pre><code>SELECT ID, 
         Firstname, 
         Lastname, 
         CASE Number 
           WHEN 0 THEN NULL 
         END
    FROM tPerson
  </code></pre>
  <p>But this results in an error:</p>
  <blockquote>
  <p>At least one of the result expressions in a CASE specification must be
  an expression other than the NULL constant.</p>
  </blockquote>