title: Two foreign keys reference one table - ON UPDATE SET NULL doesn't work
body: <p>I've got two foreign keys in a table. Let's assume that table is called <code>News</code> and has foreign keys <code>updatedById</code> and <code>createdById</code>, both of which point to <code>userId</code> in table <code>Users</code>.</p>
  
  <p>Now I want to set to <code>NULL</code> foreign keys when user is deleted, but when I try to set <code>ON DELETE SET NULL</code> in that relationships I get: </p>
  
  <blockquote>
    <p>Introducing FOREIGN KEY constraint 'FK_News_Users' on table 'News' may
    cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or
    ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.</p>
  </blockquote>
  
  <p>I don't understand why both foreign keys can't set to null?</p>