title: rails update_all fields and increment count by 1
body: <p>I have a column in my mysql table called download_count of type int.</p>
  
  <p>Now I want to use update_all to update some fields with some values, but also increment the download_count along with it.</p>
  
  <p>I have tried the following syntax:</p>
  
  <pre><code>find_record.update_all(username: username, download_date: download_date, "download_count= download_count + 1")
  </code></pre>
  
  <p>But I beleive the above acts like a where clause. So the download_count does not get updated.
  I want the username, download_date and the download_count to be updated by the above query.</p>
  
  <p>Can someone point me to the correct syntax?</p>