title: Hibernate Delete Cascade
body: <p>I Have one entity [Project] that contains a collection of other entities [Questions].</p>
  <p>I have mapped the relation with a cascade attribute of &quot;all-delete-orphan&quot;.</p>
  <p>In my DB the relation is mapped with a project_id (FK) field on the questions table. this field cannot be null since I don't want a Question without a Project.</p>
  <p>When I do <code>session.delete(project)</code> it throws an exception saying that <code>project_id</code> cant be <code>null</code>, but if I remove the <code>not-null</code> constraint to that field, the deletion works nice.</p>
  <p>Anyone knows how to solve this?</p>