title: Query to determine values not used
body: <p>I have two queries that obtain data from various tables.  Query #1 brings back data that contains ALL answers for 2 specific questions.  Query #2 returns all the possible answers (a defined list).</p>
  
  <pre><code>Table Client_Answers ca
  QuestionID      AnswerID
  1               1
  2               3
  2               3
  2               2
  1               2
  
  Table Questions q
  QuestionID      QuestionID
  1               question #1
  2               question #2
  3               question #3
  4               question #4
  
  Table Answers a
  AnswerID        Answer
  1               answer abc
  2               answer xyz
  3               answer 123
  4               answer 456
  5               answer cba
  </code></pre>
  
  <p>I am ONLY concerned about questions #1 &amp; #2 and can query for them (questions/answers) from the Table Client_Answers.  Now I need to know which possible answers available for questions #1 and #2 have never been used!
  I tried using a NOT EXISTS as follows, but it's not returning any data.</p>
  
  <pre><code>--Query #1
  SELECT q.question
  ,a.Answer
  FROM Client_Answers ca
  INNER JOIN Questions q ON q.ID = ca.QuestionID
  INNER JOIN Answers a ON a.ID = ca.AnswerID
  WHERE ca.ID IN ('1','2')
  AND NOT EXISTS
  ( --Query #2 possible answers
    SELECT 1
  FROM Answers a
  INNER JOIN Question q ON q.ID = a.QuestionID
  WHERE q.ID IN ('1','2')
  )
  </code></pre>
  
  <p>I would expect the query to return back</p>
  
  <pre><code>answer 456
  answer cba
  </code></pre>
  
  <p>What am I not doing correctly?  Not sure if I should be using an EXCEPT statement, but don't know how to use it.  This is running on SQL Server 2008.  Thank you.</p>