1. Order Database – ER Diagram
Prepared by
Greg Ashley
Fall 2016

2. Designing Databases with Entity Relationship Diagrams
Step 1: Define Entity Classes and Primary Keys
Step 2: Define Relationships Among Entity Classes
Step 3: Define Attributes for each Table
Step 4: Create Database

3. Step 1: Define Entity Classes and Primary Keys
There is not a limit to the number of orders a customer may place. Each customer can have one order, many orders, or be in your database without any orders. Each order is made by a single customer. Orders must have at least one product. Orders may have multiple products. The same product could be sold through many orders. Products can be listed in the database but not ordered by a customer.
Step 1: Define Entity Classes and Primary Keys
Entity Class
Primary Key
Customer
CustomerID
Orders
OrderID
Product
ProductID
OrderItem
Business Rules
Customer may have many orders.
2. Customers may have no orders.
3. Order can only have one customer.
4. Order must have a customer.
5. Orders must have a product.
6. Orders may have many products.
7. Products may be on many orders.
8. Products may not be on any order.

4. Step 2: Define Relationships Among Entity Classes
CUSTOMER
ORDER
Product

5. Step 3: Define Attributes for each Table
CUSTOMER
CustomerID
FirstName
LastName
Address
Major
Location
Gender
ORDER
ProductID
ProductName
Price
Type
Description
BatchSize
PRODUCT
ProductID
OrderID
Quantity

6. Step 4: Create Database