DELETE
FROM
    ORDERS_DTL
WHERE
    ORDER_NO IN 
    (
        SELECT
            ORDER_NO
        FROM
            ORDERS
        WHERE
            ORDER_DATE BETWEEN '2010/01/01' AND '2010/12/31'
    )
;

DELETE
FROM
    ORDERS
WHERE
    ORDER_DATE BETWEEN '2010/01/01' AND '2010/12/31';