delete
from ORDERS_DTL as DTL
where exists(
    select HED.ORDER_NO
        from ORDERS as HED
    where
        HED.ORDER_NO = DTL.ORDER_NO
    and HED.ORDER_DATE >= '2010-01-01'
    and HED.ORDER_DATE <= '2010-12-31'
    );

delete
from ORDERS
where ORDER_DATE >= '2010-01-01'
and  ORDER_DATE <= '2010-12-31';