title: Selecting missing entries in SQL Server
body: <p>I have a table of people:</p>
  
  <pre><code>person_id | name
  1         | bob
  2         | jane
  </code></pre>
  
  <p>A table of questions they can answer:</p>
  
  <pre><code>qu_id | question
  1     | How old are you?
  2     | How tall are you?
  </code></pre>
  
  <p>And a table of answers:</p>
  
  <pre><code>answer_id | qu_id | person_id | answer
  10        | 1     | 2         | 24
  </code></pre>
  
  <p><strong>What query will return a list of people and questions that have not been answered:</strong></p>
  
  <p>For example, Unanswered questions:</p>
  
  <pre><code>qu_id | person_id
  1     | 1
  2     | 1
  2     | 2
  </code></pre>
  
  <p>(I am using SQL Server Express 2012)</p>