title: case when null not working as expected
body: <p>consider this very short T-SQL code that does a test on a nullable column using a case</p>
  
  <pre><code>declare @t table(data varchar(10) null)
  insert into @t values('something')
  insert into @t values(null)
  
  select data, 
      case data when null
          then 'missing'
          else 'not missing'
      end as test
  from @t
  </code></pre>
  
  <p>the output that I get is:</p>
  
  <pre><code>data        test
  ---------   -----------
  something   not missing
  NULL        not missing
  </code></pre>
  
  <p>However what I was expecting was</p>
  
  <pre><code>data        test
  ---------   -----------
  something   not missing
  NULL        missing
  </code></pre>
  
  <p>What am I missing concerning the test on this nullable value</p>