Describe the relations that would be produced by the following tuple relational calculus expressions:
(a) {H.hotelName | Hotel(H) ? H.city = ‘London’}
(b) {H.hotelName | Hotel(H) ? (?R) (Room(R) ? H.hotelNo ? R.hotelNo?? R.price ?50)}
(c) {H.hotelName | Hotel(H) ? (?B) (?G) (Booking(B) ? Guest(G) ? H.hotelNo ?
B.hotelNo?? B.guestNo = G.guestNo ?? G.guestName = ‘John Smith’)}
(d) {H.hotelName, G.guestName, B1.dateFrom, B2.dateFrom | Hotel(H) ? Guest(G) ?
Booking(B1) ? Booking(B2) ? H.hotelNo ? B1.hotelNo??
G.guestNo = B1.guestNo ?? B2.hotelNo = B1.hotelNo ?
B2.guestNo = B1.guestNo ?? B2.dateFrom ? B1.dateFrom}
(a) {H.hotelName | Hotel(H) ? H.city = ‘London’}
This will produce a relation containing the names of all hotels in London.
(b) {H.hotelName | Hotel(H) ? (?R) (Room(R) ? H.hotelNo ? R.hotelNo?? R.price ?50)} This will produce a relation containing the names of all hotels that have a room price
above £50.
(c) {H.hotelName | Hotel(H) ? (?B) (?G) (Booking(B) ? Guest(G) ? H.hotelNo ?
B.hotelNo?? B.guestNo = G.guestNo ?? G.guestName = ‘John Smith’)}
This will produce a relation containing the names of all hotels that have a booking for
a guest called John Smith.
(d) {H.hotelName, G.guestName, B1.dateFrom, B2.dateFrom | Hotel(H) ? Guest(G) ?
Booking(B1) ? Booking(B2) ? H.hotelNo ? B1.hotelNo??
G.guestNo = B1.guestNo ?? B2.hotelNo = B1.hotelNo ?
B2.guestNo = B1.guestNo ?? B2.dateFrom ? B1.dateFrom}
This will produce a relation containing the names of guests who have more than one booking at the same hotel, along with the hotel number and the dates of the bookings.
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