title: SELECT DISTINCT still showing duplicates
body: <p>Yes, there's a thousand questions about this on SO, but I've been searching for half an hour and I've yet to find a solution.</p>
  
  <p>So, I've a table like this:
  <img src="https://i.stack.imgur.com/qGmMq.png" alt="enter image description here"></p>
  
  <p>And this is my query:</p>
  
  <pre><code>SELECT DISTINCT rengasID,leveys FROM renkaat ORDER BY leveys ASC
  </code></pre>
  
  <p>And this is the result I get:</p>
  
  <p><img src="https://i.stack.imgur.com/aHxoG.png" alt="enter image description here"></p>
  
  <p>If you get the idea, I'm populating a select field with it, but it still has duplicates.</p>
  
  <p>What am I doing wrong?</p>