title: Comparing a Null to another value in MySQL Trigger
body: <p>So here is my issue I am comparing new and old values when a table row is being updated. But the new or old value will sometimes be null. So the code below doesn't work. Can can I remedy this issue?</p>
  
  <p>Thank You</p>
  
  <pre><code>BEFORE UPDATE ON mytable
     FOR EACH ROW
  BEGIN
          IF OLD.assignedto != NEW.assignedto
          THEN
                  INSERT INTO history
                      (
                          asset    ,
                          changedfield     ,
                          oldvalue    ,
                          newvalue      
                      )
                      VALUES
                      (
                          NEW.asset,
                          'assignedto',
                          OLD.assignedto,
                          NEW.assignedto
                      );
          END IF;
      END$$
  </code></pre>