Consider the following AIRLINE database schema, which describes a database for airline flight information. Please illustrate all the referential constraints that hold on the schema.

Each FLIGHT is identified by a flight NUMBER, and consists of one or more FLIGHT_LEGs with LEG_NUMBERs 1, 2, 3, etc.

Each leg has arrival and departure airports and scheduled departure time and arrival time, and has many LEG_INSTANCEs--one for each DATE on which the flight travels.

LEG_INSTANCEs have actual arrival and departure times and AIRPLANE used in the instance.

FARES are kept for each flight.

For each leg instance, SEAT_RESERVATIONs are made.

An AIRPLANE is identified by an AIRPLANE_ID, and is of a particular AIRPLANE_TYPE.

CAN_LAND relates AIRPLANE_TYPEs to the AIRPORTs in which they can land.

An AIRPORT is identified by an AIRPORT_CODE.

FLIGHT_LEG Flight_number FARE AIRPLANE_TYPE AIRPLANE_TYPE CAN_LAND AIRPLANE CENT DECEDINTIONI