title: Cakephp virtual field if this column empty use this column
body: <p>I have a table named "Contacts" and I would like to create a virtual field called customer.</p>
  
  <p>Contacts has column, called first_name, last_name, company.</p>
  
  <p>I got it to work creating virtual field by concatenate all three</p>
  
  <pre><code>public $virtualFields = array(
  'customer' =&gt; "CONCAT(Contact.first_name, ' ', Contact.last_name, ' ', Contact.company)"        
  );
  </code></pre>
  
  <p>but how can I create it so it instead just show the company, but if it's null or empty string, it will show the first name and last name</p>