title: Spark SQL Datediff between columns in minutes
body: <p>I have 2 columns in a table (both dates, formatted as string type). I need to find difference between them in minutes and then average the difference over an year.</p>
  <p>Format as below:
  Requesttime: 11/10/2019 03:10:15 PM
  Respondtime: 11/10/2029 03:20:10 PM</p>
  <p>Any suggestions?</p>