title: isnull vs is null
body: <p>I have noticed a number of queries at work and on SO are using limitations in the form:</p>
  
  <pre><code>isnull(name,'') &lt;&gt; ''
  </code></pre>
  
  <p>Is there a particular reason why people do that and not the more terse</p>
  
  <pre><code>name is not null
  </code></pre>
  
  <p>Is it a legacy or a performance issue?</p>