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Chapter 7: Problem 20

Consider a company that owns and operates parking lots. Develop an ERD with two entity types Parking Lot and Space and where: The address of a parking lot serves to identify the lot. Each space within a lot is rented at the same monthly rental charge. Each parking space is known by its number within the lot (within a lot these always start at 1). Each parking space is rented out to at most one vehicle. The vehicle’s identifier must be recorded. The identifier comprises a province code and license plate number.

Short Answer

Expert verified
The ERD for the parking lot scenario has three entities: Parking Lot, Space, and Vehicle. Parking Lot has an attribute 'Address' which is a key. Space has attributes 'Number' and 'Rental Charge', with 'Number' acting as a key. There's a one-to-many relationship from Parking Lot to Space and a one-to-one relationship from Space to Vehicle. Vehicle's identifier, made up of 'Province Code' and 'License Plate Number' and specific to each Space, must be recorded.

Step by step solution

01

Identify Entities

Entities can be objects or concepts that are describable and identifiable. From the exercise, the entities we have are 'Parking Lot' and 'Space'.
02

Identify Attributes

Attributes are properties or characteristics of entities. For the 'Parking Lot' entity, the attribute is 'Address', which also serves as a unique identifier (i.e., a key). For the 'Space' entity, the attributes are 'Number' and 'Rental Charge'. As described, each 'Space' is identified by a unique 'Number' within a 'Parking Lot'.
03

Identify Relationships

Relationships connect entities. In this exercise, we're given that each 'Parking Space' is rented out to at most one 'Vehicle'. Thus, a 'Vehicle' is another entity, and the relationship between 'Space' and 'Vehicle' is a one-to-one relationship. The 'Vehicle' entity has an identifier made of 'Province Code' and 'License Plate Number'.
04

Draw ERD

Draw the ERD with 'Parking Lot', 'Space', and 'Vehicle' as entities. Include attributes for each entity and mark their keys. Show the relationships between entities: one-to-many from 'Parking Lot' to 'Space', as there can be multiple spaces in a parking lot, and one-to-one between 'Space' and 'Vehicle', as a space can be rented to at most one vehicle. The relationship between 'Space' and 'Vehicle' should also indicate that the vehicle's identifier must be recorded.

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Most popular questions from this chapter

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.

Draw an ERD involving employees and their dependents where each employee has a unique id number and where dependents of the same employee are numbered starting at 1. It may be rare, but we will allow for dependents of the same employee to have the same name and birthdates. Include typical attributes for an employee, and for a dependent include the birthdate, first and last names.

Consider a requirement having to do with benefits that may be given to employees of a company. Suppose employees work in a department and that each employee may have several dependents (spouse, child). Draw an ERD that includes Department, Employee, and Dependent in your design. Include attributes for your entity types.

A birthdate attribute would appear for many entity types – for example students, employees, children. What is a birthdate likely to be: key or non- key?

Suppose a company that sells products has a product entity type with the following attributes: prodNum, prodDesc, prodPrice. Suppose all three attributes are single-valued and that prodNum is a key attribute - each product has a different product number. Illustrate this information in an ERD.
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