title: Remove specific fields and show other fields in Mysql
body: <p>I would like to ask for ways to solve this MySQL issue. 
  Currently, I have this select query <br></p>
  
  <pre><code>SELECT username, friend_username from friends
  WHERE (username = "apple" or friend_username = "apple");
  </code></pre>
  
  <p>and it shows this <strong>Friends</strong> Table (below).</p>
  
  <pre><code>Friends Table
  ------------------------------
  | username | friend_username |
  ------------------------------
  | apple    | orange          |
  | apple    | pear            |
  | durian   | apple           |
  ------------------------------
  </code></pre>
  
  <p>But I would like to execute a select query to make it look like this (below).</p>
  
  <pre><code>------------
  | username |  
  ------------
  | orange   |
  | pear     |
  | durian   |
  ------------
  </code></pre>
  
  <p>Is there any possible ways to achieve this? Appreciate the help! Thank you.</p>