oracle sql newbie question

I appreciate if somebody help me with following question.

Why following two statements give different order?

SQL> select * from orders
  2 where (prod_id, cust_id ) in
  3 (select prod_id, cust_id from orders)   4 /

ORD_DATE PROD_ID CUST_ID QUANTITY PRICE DISCOUNT
--------- ---------- ------- ---------- ---------- ----------

20-FEB-00       1001 B0134           25    2065.85         50
20-FEB-00       1001 B0135            3      247.9          6
20-FEB-00       1741 B0134            5       65.5

ORD_DATE PROD_ID CUST_ID QUANTITY PRICE DISCOUNT
--------- ---------- ------- ---------- ---------- ----------

20-FEB-00       1741 B0134            5       65.5
20-FEB-00       1001 B0134           25    2065.85         50
20-FEB-00       1001 B0135            3      247.9          6

Thank you in advance,

Tom Gong Received on Sun Mar 11 2001 - 15:01:02 CET