title: How to avoid the duplicate value while joing two tables?
body: <p>I am preparing a questionnaire in <strong>code-igniter</strong> frame work.At a time one question is displayed for answering.The answered questions are entered into a temporary table.If the page is refreshed already answered questions are again displayed.For that I tried to join the temporary table and main table but its not working.I used the following query,</p>
  
  <pre><code>"SELECT a.boxes FROM quest a LEFT JOIN useranswer1 b ON  a.boxes!=b.question"
  </code></pre>
  
  <p>quest is main table and useranswer1 is temporary table.</p>
  
  <p>The result contain all the values in the main table(<code>quest</code>). I need the values which are not in the <code>useranswer1</code>(temporary table). Is it possible using join query or any other method?</p>