Question

Wally Los Gatos, owner of Wally's Wonderful World of Wall coverings, has hired you asa consultant to design a database management system for his chain of three stores that sells wallpaper and accessories. He would like to track sales, customers, and employees. After aninitial meeting with Wally, you have developed a list of business and specifications to begin the design of an E-R model:_____________.

Answer 1

Answer: In order to design an ER model we have to do the following steps:

1. Identify the entities:

- Customers

- Employees

- Sales

2. Atributes:

- Customers

ID

Name

Age

Adress

Nationality

Credit limit

- Employees

ID

Name

Age

Adress

Nationality

Salary

Position

Amount of sales

- Sales

Id_Sales

Date

Invoice

Id_Product

Quantity

Unit Price

Total

Tax

Id_Customer

Id_Employees

Sales commission

3. Relationships:

- An employee can make many sales.

- Also, a customer can have many sales.

- An employee will earn a commission from a sale.

4. Primary Keys:

- ID (Customers and employees)

- Id_Sales

5. Foreign Keys:

- Id_Customers

- Id_Employees

Explanation: The Entity-Relationship Model (ER) is a basis design methodology of Data that consists in representing at a conceptual level the data that support the operation of a system.

The basic components of a MER are:

1. Entities: Represents an object with a physical existence, in this case, customers, employees and sales.

2. Attributes: Represents the caracteristics of an entity. An employee will have a name and ID, also an adress and salary.

3. Relationships: Represents the association between entities and how they work each other, for example, the posibility of the same employee making several sales.