触发器中old与new含意

create trigger trigger1 after insert on t_book for each row

 update t_booktype set bookNum=bookNum+1 where id=new.bookTypeId;  

drop trigger trigger2;

delimiter |
create trigger trigger2 after delete on t_book for    each row
        begin
        update t_booktype set bookNum=bookNum-1 where id=old.bookTypeId;
        insert into t_log values(1,now());
        end
        |
delimiter ;

new 代表刚创建的行，old刚删除的行