create table grade_change_history
(time_stamp date,
stu_id number(7,0),
class_id number(6,0),
enroll_date date,
old_final_grade char(1),
new_final_grade char(1)
);



create or replace trigger audit_grade_change
after update of final_letter_grade on enrollments
for each row
begin
insert into grade_change_history(old_final_grade,new_final_grade)
values(:OLD.final_letter_grade, :NEW.final_letter_grade);
end;

select * from enrollments

select * from grade_change_history

update enrollments
set final_letter_grade='B'
where stu_id=102;
