title: SQL Distinct keyword bogs down performance?
body: <p>I have received a SQL query that makes use of the <code>distinct</code> keyword. When I tried running the query it took at least a minute to join two tables with hundreds of thousands of records and actually return something.</p>
  <p>I then took out the distinction and it came back in 0.2 seconds. Does the distinct keyword really make things that bad?</p>
  <p>Here's the query:</p>
  <pre><code>SELECT DISTINCT
      c.username, o.orderno, o.totalcredits, o.totalrefunds,
      o.recstatus, o.reason 
  FROM management.contacts c 
      JOIN management.orders o ON (c.custID = o.custID)
  WHERE o.recDate &gt; to_date('2010-01-01', 'YYYY/MM/DD')
  </code></pre>