title: Salesforce equivalent of "SELECT DISTINCT"?
body: <p>I want to know what all the existing values of a field are.</p>
  
  <p>In SQL that would be something like:</p>
  
  <pre><code>SELECT DISTINCT foo
  FROM bar
  </code></pre>
  
  <p>How might I do this with salesforce's SOQL?</p>