Respuesta :
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.
