title: COALESCE vs IS NOT NULL performance on checking empty string
body: <p>Some articles I found on the internet compared ISNULL with COALESCE, so I think my question is a little different.</p>
  
  <p>I'm wondering which is better <em>in terms of performance</em>?</p>
  
  <pre><code>SELECT * FROM mytable WHERE mycolumn IS NOT NULL AND mycolumn &lt;&gt; '';
  </code></pre>
  
  <p>Or</p>
  
  <pre><code>SELECT * FROM mytable WHERE COALESCE(mycolumn,'') &lt;&gt; '';
  </code></pre>
  
  <p>Other than performance, are there any other concerns I should consider when deciding?</p>
  
  <p>EDIT:</p>
  
  <p>I'm using Teradata.</p>