title: Counting the appearances in rows for a given value
body: <p>I have a table called <code>private_message</code> with the fields: <code>sender</code> and a <code>receiver</code></p>
  
  <p>I would like to know how many times a specific sender has send a message to a given person, for instance:</p>
  
  <pre><code>**Name**     **Times**
  David        5
  Michael      2
  John         1
  </code></pre>