title: how to create a trigger in concatenating a auto_increment value column and a column that has a default value
body: <pre><code>DELIMITER $$
  CREATE DEFINER=`root`@`localhost` TRIGGER `grade_one_BINS`
   BEFORE INSERT ON `grade_one` FOR EACH ROW
  set new.student_no = concat(new.letter, ' - ',new.num)
  </code></pre>
  
  <p>there is a problem in concatenating the num column that has auto increment value since the trigger is for before insert cause it will show a 0 value since the auto increment is still 0 until you insert some values...can you help me???</p>