title: How can I increment a column by one in a trigger?
body: <p>I need help writing a MySQL trigger.</p>
  
  <p>Suppose you have a student database with the following tables:</p>
  
  <pre><code>ENROLLMENT(SSN, CLASS_NO, GRADE)
  CLASS(CLASS_NO, CLASS_TITLE, NO_OF_STUDENTS).
  </code></pre>
  
  <p>I need to write a trigger to increase the <code>NO_OF_STUDENTS</code> by one if a new student is added to the <code>ENROLLMENT</code> table for that <code>CLASS_NO</code>.</p>