View UNION help required - CLOSED

CLOSED:

Thank you Sagar. The Views UNION as described below was successful as built with the recommendations below. In the end with the real queries, it did not seem to be practical.

The better solution was to rewrite the Content Types so that they could both be manipulated through the same View query.

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I have two Views queries in hook_views_pre_execute that display correctly.
I am trying to display the superset of both queries using a UNION similar to:

function custom_views_pre_execute(&$view) {
  if ($view->name == "my_view") {
    $query1 = db_select('node', 'node');
    $query1->addField('node', 'title', 'node_title');
    $query1->addField('node', 'nid', 'nid');

    $query2 = db_select('node', 'node');
    $query2->addField('node', 'title', 'node_title');
    $query2->addField('node', 'nid', 'nid');

    $query=Database::getConnection()
      ->select($query1->union($query2))
      ->fields(NULL, array('node_title', 'nid'));

    $view->build_info['query'] = $query2;
    $view->build_info['count_query']=$view->build_info['query'];
  }
}

Unfortunately, the result is not displaying correctly.

I require help to correct this. I think the problem is either in the above hook or in the View itself.