create table tmp_tbl2(
u_id        varchar2(10),
wdate       date,
n_sub_no    char(3),
n_stu_no    varchar2(9),
n_enr_grade number(3),
o_sub_no    char(3),
o_stu_no    varchar(9),
o_enr_grade number(3),
bigo        char(1)
);

create or replace trigger tri4
    after insert or update or delete
    on enrol
    for each row
    begin
        if inserting then
            insert into tmp_tbl2(u_id, wdate, n_sub_no,n_stu_no, n_enr_grade, bigo)
                values(user,sysdate,:new.sub_no,:new.stu_no, :new.enr_grade, 'I');
                
        elsif updating then
            insert into tmp_tbl2(u_id, wdate, o_sub_no,o_stu_no, o_enr_grade,n_sub_no,n_stu_no, n_enr_grade bigo)
                values(user,sysdate,:old.sub_no, :old.stu_no, :old.enr.grade, :new.sub_no, :new.stu_no, :new.enr_grade, 'U');
        
        elsif deleting then
            insert into tmp_tbl2(u_id,wdate,o_sub_no,o_stu_no,o_enr_grade,bigo)
                values(user,sysdate,:olf.sub_no,:old.stu_no,:old.enr_grade,'D')
        end if;
end tri4;

분명히 책 실습나온 코드대로 쳤는데 왜 에러가 발생하는지 모르겠어요