title: Group by Count of DateTime Per Hour by removing Duplicates?
body: <p>I have a table named loginData:</p>
  <pre><code>userName timestamp
  abc      '2007-01-01 12:00:12 AM'
  def      '2021-01-01 12:09:12 AM'
  abc      '2021-01-01 12:40:12 AM'
  abcde    '2021-01-01 12:44:12 AM'
  </code></pre>
  <p>From this table I want to query the data in such a way that It doesn't count duplicates. I want to get data like this:</p>
  <pre><code>userLoggedIN - 3
  </code></pre>
  <p>Considering <code>abc</code> has logged in twice to count it as one. How to do this?</p>