DELETE FROM ORDERS_DTL
WHERE
  ORDER_NO IN (
    SELECT
      ORD.ORDER_NO
    FROM
      ORDERS AS ORD
      LEFT JOIN ORDERS_DTL AS DTL ON ORD.ORDER_NO = DTL.ORDER_NO
    WHERE
      ORD.ORDER_DATE BETWEEN '20100101' AND '20101231'
  );

DELETE FROM ORDERS
WHERE
  ORDER_DATE BETWEEN '20100101' AND '20101231';

SELECT
  *
FROM
  ORDERS AS ORD
  LEFT JOIN ORDERS_DTL AS DTL