title: Selection without duplicates. The same data, but different order
body: <p>I have some query that returns this:</p>
  
  <pre><code>model   model   speed   ram
  1121    1233    750 128
  1232    1233    500 64
  1232    1260    500 32
  1233    1121    750 128
  1233    1232    500 64
  1260    1232    500 32
  </code></pre>
  
  <p>I don't need repeating data as:</p>
  
  <pre><code>1121    1233    750 128
  1233    1121    750 128
  </code></pre>
  
  <p>It's the same, but with different order of models.</p>
  
  <p>All data stores in one table. There are a lot of PC's which have various models. I need PC's which have the same speed and ram, but I have some problem (described above).
  Here's my query:</p>
  
  <pre><code>SELECT a.model, b.model, a.speed, a.ram
  FROM PC AS a, PC AS b
  WHERE a.speed = b.speed AND a.ram = b.ram AND a.model != b.model
  ORDER BY a.model DESC, b.model ASC
  </code></pre>