UNION support

I need union to merge several queries in views, but I cannot find anything inside views that references union. Is this not possible?

Here is an example that I'd like to migrate to a view:

  $ignore_response_codes = preg_split('/(\r\n?|\n)/', variable_get('linkchecker_ignore_response_codes', "200\n206\n302\n304\n401\n403"));

  // Search for broken links in nodes and comments and blocks of all users.
  // @todo Try to make UNION'ed subselect resultset smaller.
  $subquery4 = db_select('linkchecker_node', 'ln')
    ->distinct()
    ->fields('ln', array('lid'));

  $subquery3 = db_select('linkchecker_comment', 'lc')
    ->distinct()
    ->fields('lc', array('lid'));

  $subquery2 = db_select('linkchecker_block_custom', 'lb')
    ->distinct()
    ->fields('lb', array('lid'));

  // UNION all linkchecker type tables.
  $subquery1 = db_select($subquery2->union($subquery3)->union($subquery4), 'q1')->fields('q1', array('lid'));

  // Build pager query.
  $query = db_select('linkchecker_link', 'll')->extend('PagerDefault')->extend('TableSort');
  $query->innerJoin($subquery1, 'q2', 'q2.lid = ll.lid');
  $query->fields('ll');
  $query->condition('ll.last_checked', 0, '<>');
  $query->condition('ll.status', 1);
  $query->condition('ll.code', $ignore_response_codes, 'NOT IN');

If UNION is really missing, this need to be added to views. It's really common SQL.