Imagine you are the database administrator for a military transportation system. You

have a table named cargo in your database that contains information on the various

cargo holds available on each outbound airplane. Each row in the table represents a

single shipment and lists the contents of that shipment and the flight identification

number. Only one shipment per hold is allowed. The flight identification number may

be cross$-$referenced with other tables to determine the origin, destination, flight time,

and similar data. The cargo table appears as follows:

Flight ID Cargo Hold Contents Classification

$1254$ A Boots Unclassified

$1254$ B Guns Unclassified

$1254$ C Atomic bomb Top Secret

$1254$ D Butter Unclassified