I have a query about a hotel's room booking system.
Please take a look into the room table.

The following is the order table:

What query would fetch me the date(s) which has all rooms (8 in this case) booked on that date?
For this case it would be 2010-12-10 and 2010-12-20, since all 8 rooms have been booked for the date.

Please if anyone can help?
Many thanks in advance

