title: Show Sum of Columns in Pie Chart Drupal
body: <p>I used <a href="https://www.drupal.org/project/google_chart_tools" rel="nofollow">Google Chart Tools</a> in Drupal.</p>
  
  <p>I have 3 columns in a dataset with integer values. I want to show the sum of each column, in a pie chart.</p>
  
  <p>I tried putting Sum(field1), Sum(field2), ... in value fields, but it doesn't work correctly and creates several series. How can I do that?</p>