title: Update column in table to two concatenated columns
body: <p>I have 3 columns in a table 
  <code>paxname</code> <code>fname</code> <code>lname</code>
  now i want to concatenate <code>fname</code> and <code>lname</code> 
  and update that in paxname</p>
  
  <p>My following query did not work</p>
  
  <pre><code>update pax set paxname =lname || " " || fname
  </code></pre>
  
  <p>I tried with CONCAT function but it didnt work either.</p>