Question

Create an Entity‐Relationship Diagram that will show the relationship between the
entities that will be present in the canteen application. Your diagram should
indicate the following:
 Cardinality
 Primary Keys
 Foreign Keys
 At least one attribute other than the primary or foreign key.

Answer 1

Here is an Entity-Relationship Diagram for the canteen application:

Entities:
1. Customer
2. Order
3. Menu Item
4. Payment

Relationships:
1. Customer places Order (1 to many)
2. Order contains Menu Item (many to many)
3. Order has Payment (1 to 1)

Cardinality:
- Customer can place multiple Orders, but each Order is placed by only one Customer. (1 Customer: many Orders)
- Each Order can contain multiple Menu Items, and each Menu Item can be part of multiple Orders. (many Orders: many Menu Items)
- Each Order has only one Payment, and each Payment belongs to only one Order. (1 Order: 1 Payment)

Primary Keys:
- Customer: Customer ID
- Order: Order ID
- Menu Item: Menu Item ID
- Payment: Payment ID

Foreign Keys:
- Order: Customer ID (refers to Customer entity)
- Order: Menu Item ID (refers to Menu Item entity)
- Payment: Order ID (refers to Order entity)

Attribute:
- Menu Item: Price (other than primary or foreign key)