title: How to use isset condition for mysql query output
body: <p>I get some data from MySQL, and I print the data as <code>echo $row['ref'];</code>.</p>
  
  <p>Sometimes <code>echo $row['ref'];</code> returns empty result. I want to compose a condition like <code>echo isset($row['ref']) ? $row['ref']:'Unknown';</code> which will show <code>Unknown</code> word if <code>echo $row['ref'];</code> returns empty result.</p>
  
  <p>Thanks in advance.</p>