Views, getting nodes type 1 which user have NO node of type 2 published that references the node type 1

Question

I'm using drupal 7.20 with Views 3 module.

I've a content type "Homework" and a content type "Solution". The Solution content type has an entity reference field that references nodes of type "Homework".

Well, I'm trying to set up with Views a new Tab in the user profile menu: "Pending Homeworks" that lists all Homeworks that has no Solution referencing them and published by that user.

Best an example:

"Homework 1" <- "Solution (by user 1)"
             <- "Solution (by user 2)"
             <- "Solution (by user 3)"

"Homework 2" <- "Solution (by user 1)"
             <- "Solution (by user 3)"

"Homework 3" <- "Solution (by user 3)"

In this example, user 2 hasn't published yet his Solution for Homework 2 and Homework 3, so, the View I want, must output: Homework 2 and Homework 3.

Thanks in advance.

Answer 1

This has already been answered here.

A simple view will not do what you want.

Answer 2

Thank you, Triskelion, for pointing me in the right direction.

Finally, I've set up a block with PHP and a single query:

<?php
global $user;
if (isset($user->uid)) {
  // Get uid of user logged in
  $x_uid = $user->uid;
  // If user is not empty or 0
  if ($x_uid) {
    // Subselect: Get desafio nids that have solutions published by $x_uid
    $select2 = db_select('field_data_field_enlace_al_enunciado','r');
    $select2->leftjoin('node','no','r.entity_id = no.nid');
    $select2->fields('r',array('field_enlace_al_enunciado_target_id'))
      ->condition('no.uid',$x_uid);
    // Get all desafio nids that are not in subselect
    $select = db_select('node','n')
      ->fields('n',array('nid','title'))
      ->condition('type','desafio')
      ->condition('n.nid',$select2,'NOT IN');
    // Execute the whole query
    $result = $select->execute();
    // Get results and print them out
    while ($record = $result->fetchAssoc()) {
      print '<a href="/'.drupal_get_path_alias('node/'.$record['nid']).'">'.$record['title'].'</a><br/>';
    }
  }
}
?>

It works! ;-)