5.12 Database Consider the AIRLINE relational database schema shown in Figure 5.8, which describes a database for airline flight information. Each FLIGHT is identified by a Flight_number, and consists of one or more FLIGHT_LEGs with Leg_numbers 1, 2, 3, and so on. Each FLIGHT_LEG has scheduled arrival and departure times, airports, and one or more LEG_INSTANCEs one for each Date on which the flight travels. FAREs are kept for each FLIGHT. For each FLIGHT_LEG instance, SEAT_RESERVATIONs are kept, as are the AIRPLANE used on the leg and the actual arrival and departure times and airports. An AIRPLANE is identified by an Airplane_id and is of a particular AIRPLANE_TYPE. CAN_LAND relates AIRPLANE_TYPEs to the AIRPORTs at which they can land. An AIRPORT is identified by an Airport_code. Consider an update for the AIRLINE database to enter a reservation on a particular flight or flight leg on a given date. a. Give the operations for this update. b. What types of constraints would you expect to check? c. Which of these constraints are key, entity integrity, and referential integrity constraints, and which are not? d. Specify all the referential integrity constraints that hold on the schema shown in Figure 5.8.

AIRPORT Airport code Name City State FLIGHT Flight number Airline Weekdays FLIGHT LEG Right number Leg number Departure airport code Scheduled departure time Arrival airport code Scheduled arrival time LEG INSTANCE Flight number Leg number Date Number of available seats Airplane id Departure airport code Departure time Arrival airport code Arrival time FARE Right number Fare code Amount Restrictions AIRPLANE TYPE Airplane type name Max seats Company CAN LAND Airplane type name Airport code AIRPLANE Airplane d Total number of seats Airplane type SEAT RESERVATION Light numbor numbord Seat number Customer nane Customer phone Figure 5.8 The AIRLINE relational database schema