delete
from orders as os1
where os1.order_no in (
    select
        os2.order_no
    from orders as os2
    where os2.order_date between '2010-01-01' and '2010-12-31'
);

delete
from orders_dtl as od1
where od1.order_no in (
    select
        os.order_no
    from orders as os
    left join orders_dtl as osd on os.order_no = osd.order_no
    where os.order_date between '2010-01-01' and '2010-12-31'
);