title: Operand should contain 1 column(s) MySQL
body: <p>does anyone knows what's going on with this query please ?. What I am trying to do is if <code>courseID</code> in <code>elective_modules</code> table <em>doesn't exist</em> in <code>group_elective_modules</code> table, then print all  exit in <code>group_elective_modules</code>. But I keep getting the error <strong>Operand should contain 1 column(s)</strong></p>
  
  <p><strong>Here is my query</strong></p>
  
  <pre><code>$alternativeEQuery = 
  "SELECT elective_modules.courseID,elective_modules.yr 
   FROM elective_modules
   WHERE elective_modules.yr = '$year1' 
   AND elective_modules.courseID 
   NOT IN 
       (SELECT group_elective_modules.moduleID,group_elective_modules.courseName 
   FROM group_elective_modules 
   WHERE group_elective_modules.courseName = '$courseTitle'
   AND elective_modules.courseID = group_elective_modules.moduleID)";
  
  $alternativeEResult = mysql_query($alternativeEQuery) or die($alternativeEQuery."&lt;br/&gt;&lt;br/&gt;".mysql_error());
  </code></pre>