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Chapter 7: Problem 25

Consider a company that owns and operates parking lots. Draw an ERD to include the following specifications. Each parking lot has a unique address (use the typical fields for addresses) and each parking lot has a certain number, say n, of parking spaces. Each space in a lot has a number between 1 and n. The cost of renting a parking space is the same for all spaces in a lot. The company rents individual spaces out to its customers. Each customer is identified by a driver’s license id, has a first and last name. Each customer will identify possibly several cars that they will park in the space rented to them. For each car the company needs to know the year, make, model, colour and its license plate number.

Short Answer

Expert verified
The ERD should include four entities ('Parking Lot', 'Parking Space', 'Customer', 'Car'), each with its specific attributes. The relationship among them should be represented in accordance to the given specifications.

Step by step solution

01

Identifying Entities

The first step is identifying the entities. In this case, the entities are 'Parking Lot', 'Parking Space', 'Customer' and 'Car'.
02

Identifying Attributes

The second step is identifying the attributes for each entity. 'Parking Lot' has attributes 'Address' and 'Number of Spaces', 'Parking Space' has attributes 'Space number' and 'Rental Cost', 'Customer' has attributes 'Driver’s License ID', 'First Name', 'Last Name'. 'Car' has attributes 'Year', 'Make', 'Model', 'Color', and 'License Plate Number'.
03

Identifying Relationships

The third step is identifying the relationships between these entities. 'Customer' rents 'Parking Space'. 'Customer' identifies 'Car'. The relationship between 'Parking Space' and 'Parking Lot' could be represented as 'Parking Space' is located in 'Parking Lot'.
04

Draw the ERD

Based on the relationships and attributes, draw the ERD. Each entity should be represented as a rectangle and its attributes as ellipses connected to the rectangle. Relationships should be represented as diamonds connecting the related rectangles with lines.

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Most popular questions from this chapter

Assuming you have experience with some database system, what data type would you use for surrogate keys?

Consider an ERD for modelling customers, phones, and phone calls. Each customer owns one phone and so the phone number identifies the customer. Include other attributes such as credit card number, first name, and last name for a customer. We must record information for each phone call that is made: for each call there is a start time, end time, and of course the phone number/customers involved.

Consider a marriage entity type and attributes marriage date, marriage location, husband, wife. Each marriage will only have one value for each of these attributes. Illustrate the marriage entity and its single-valued attributes in an ERD .

Consider the one-to-one operates relationship in this chapter. Modify the example so that drivers have attributes: driver license, name (which comprises first name and last name), and vehicles have attributes: license plate number, VIN, year, colour, make and model. Note that VIN stands for vehicle identification number and this is unique for each vehicle. Assume that each driver must be assigned to a vehicle.

Develop an ERD to be used by a company to manage the orders it receives from its customers. Each customer is identified uniquely by a customer id; include the first name, last name, and address for each customer. The company has several products that it stocks and for which customers place orders. Each product has a unique id, unique name, unit price, and a quantity on hand. At any time a customer may place an order which will involve possibly many products. For each product ordered the database must know the quantity ordered and the unit price at that point in time. If the customer does this through a phone call then an employee is involved in the call and will be responsible for the order from the company side. Some orders are placed via the internet. For each order an order number is generated. For each order the database must keep track of the order number, the date the order was placed and the date by which the customer needs to receive the goods.
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