Consider lucky Rent-A-Car’s website, which contains its database, as described in figure 5.18. Describe, in detail, the steps taken in both hardware and software to reach the database when a customer is making a reservation for rental car over the web.
Figure 5. 18 shows the relationship database for the lucky Rent-A-Car example described earlier. There is a one- to-many relationship from manufacturers to cars and another one- to- many relationship from cars to maintenance events. The former requires the manufacturer primary key. Manufacture name, to be placed in the car relation as a foreign key. The latter requires the car primary key. Car Serial Number, to be placed in the Maintenance relation as a foreign key. The many- to- many relationship among cars and customers requires the creation of a new relation, the rental relation. Each record of the Rental relation records the rental of a particular car by particular customer. Note that the combination of the Car Serial Number and Customer Number attributes is not sufficient as the primary key of the rental relation. A given customer might have rented a given car more than once. Adding Rental Date to the primary key achieve the needed uniqueness.