title: Drupal views multiple sort criteria
body: <p>I have multiple content types in drupal and they both use different date fields. One is using blog_date and second post_date. When I merge them in one view and try to sort by multiple sorting criterias, they are always sorted by the first one. I.e. if I sort by blog_date first, all blog type posts will appear and only after that post type posts will follow with their sorting criteria.</p>
  
  <p>Is it possible to merge those two data fields into one and then sort nodes globally?</p>