title: Format of Date_Trunc in SQL (Redshift)
body: <p>The below works:</p>
  <pre><code>SELECT DATE_TRUNC('day', TIMESTAMP '2017-03-17 02:09:30')
  </code></pre>
  <p>But if I remove the &quot;TIMESTAMP&quot; part (as below) it doesn't. Why is this?</p>
  <pre><code>SELECT DATE_TRUNC('day', '2017-03-17 02:09:30')
  </code></pre>
  <p>From what I understand, the format should just be:</p>
  <pre><code>DATE_TRUNC('datepart', timestamp)
  </code></pre>
  <p>This simple format works in other situations..</p>