title: Select distinct rows by multiple columns and retrieve yet another column which is not taking part in determining the distinctness
body: <p>So here's how I select distinct rows by a combination of multiple columns (a, b and c):</p>
  
  <pre><code>select distinct a,b,c from my_table
  </code></pre>
  
  <p>This is good, but I need yet another column retrieved for these rows (d) which I can't add to the select part, because then it also plays a role in determining row uniqueness which I don't want.</p>
  
  <p>How can I retrieve an additional column without it affecting row uniqueness?</p>