这个触发器怎么写？着急呀！请高手帮忙看看！！！

create or replace trigger trig_name
    after insert or update or delete on invoice
    for each row
begin
    if INSERTING then
        insert into tag(..) values(:new.id,'invoice',0);
    elsif UPDATING then
        insert into tag(..) values(:old.id,'invoice',1);<--更新的记录原来值
    else
        insert into tag(..) values(:old.id,'invoice',2);
    end if;
end;