title: Data from a joined table where the join table doesn't have an entry
body: <p>I have a table of answers, and a table of questions, and a join table to join them. The quesions table has questions, and the answers table has answers to those questions. The problem being, this is a multi choice setup. So the answers will have some right answers and some wrong answers for a question. </p>
  
  <p>Whether an answer is right or not is indicated by a boolean - is_right. </p>
  
  <p>How can I find which quesions have answers where there <em>isn't</em> a right answer (and similarly, where there isn't a wrong answer) in the answers table?</p>