title: Variables from a table that not exist in another one
body: <p>Hello everybody i am currently trying to get the variables from one table that not exist in a second in mysql , for example i have this code </p>
  
  <pre><code>SELECT students.`StudentID`
  From students
  JOIN studentsdays ON studentsdays.`StudentID`=students.`StudentID`
  JOIN studentshours ON studentshours.`StudentID`=students.`StudentID`
  JOIN studentclassroom ON studentclassroom.`StudentID`=students.`StudentID`
  JOIN attendance ON attendance.`StudentID` = students.`StudentID`
  WHERE dayID='14mon' and hoursid='ora2' and ClassRoomID=101 and CourseID =1111
  </code></pre>
  
  <p>Which displays the following table </p>
  
  <pre><code>StudentID
  ----------
   11111
  ----------
   22222
  ----------
   33333   
  </code></pre>
  
  <p>The second code </p>
  
  <pre><code>SELECT user_id FROM demo_log
  </code></pre>
  
  <p>Displays the following table</p>
  
  <pre><code>user_id
  ----------
   11111
  ----------
   22222
  </code></pre>
  
  <p>How can i put this codes together to get a table that will have the values that are only on the first table , give a table like this one </p>
  
  <pre><code>StudentID
  ----------
   33333   
  </code></pre>