title: Find possible duplicates in two columns ignoring case and special characters
body: <h3>Query</h3>
  <pre><code>SELECT COUNT(*), name, number
  FROM   tbl
  GROUP  BY name, number
  HAVING COUNT(*) &gt; 1
  </code></pre>
  <p>It sometimes fails to find duplicates between lower case and upper case.<br />
  E.g.: <code>sunny</code> and <code>Sunny</code> don't show up as a duplicates.<br />
  So how to find all possible duplicates in PostgreSQL for two columns.</p>