Problem 12.1 [6] Write a TRIGGER to ensure that DEPT TABLE does not contain duplicate of null values in DEPTNO column. Problem 12.2 [6] Write a Trigger to carry out the following action on deleting a deptno from dept table, all the records with that deptno has to be deleted from the emp table Problem 12.3 [6] Write a Trigger to carry out the following action: on deleting any records from the emp table, the same values must be inserted into the log table