title: Count entries that have different values in other column
body: <p>Here is an (simplified) example of DB I have (sorry for the ulgy format, I don't know how to write tables):</p>
  
  <pre><code>Name | Num  
  John | 1  
  John | 3  
  John | 4  
  Dany | 2  
  Andy | 5  
  Andy | 5 
  </code></pre>
  
  <p>I want to count how many people have more at least two different Numbers.</p>
  
  <p>For instance, here, only john, because he has <code>1</code>, <code>3</code> and <code>4</code>.<br>
  Not Andy because he has twice 2 and no other one.<br>
  And obviously not Dany because he has only one entry.</p>
  
  <p>Thank you very much.</p>