23.18 Again using the Hotel schema, draw a relational algebra tree for each of the following queries and use the heuristic rules given in Section 23.3.2 to transform the queries into a more efficient form. Discuss each step and state any transformation rules used in the process.

(a)

SELECT r.roomNo, r.type, r.price

FROM Room r, Booking b, Hotel h

WHERE r.roomNo = b.roomNo AND b.hotelNo = h.hotelNo AND

h.hotelName = Grosvenor Hotel AND r.price > 100;

(b)

SELECT g.guestNo, g.guestName

FROM Room r, Hotel h, Booking b, Guest g

WHERE h.hotelNo = b.hotelNo AND g.guestNo = b.guestNo AND h.hotelNo = r.hotelNo AND

h.hotelName = Grosvenor Hotel AND dateFrom >= 1-Jan-08 ANDdateTo <= 31-Dec-08;