Using ER Assistant (recommended) or Visio, create an ER diagram (ERD) that has at least 5 entities but no more than 6 entities

Using ER Assistant (recommended) or Visio, create an ER diagram (ERD) that has at least 5 entities but no more than 6 entities. Each entity must have a minimum of 5 attributes that fully describe that entity. The 5 attribute minimum includes the primary key only (see note below about foreign keys in ER diagrams).

All entities must be connected with suitable relationships that describe not only the cardinality (1:1, 1:M, M:M) but also whether the relationship is mandatory or optional.

Every entity and relationship in your diagram must have comments describing your business rules, i.e. the purpose of the entity and attributes, its relationship cardinality, and if it is mandatory or optional. You may embed these comments into the ERD using ‘Design Notes’/‘Design Justification’ inserts or provide them in a separate Word document.

Crow’s Feet notation style is required for all relationships. If you use ER Assistant, this is the default notation style. If you use Visio, you must ensure that you properly set the use of Crow’s Feet notation prior to submitting your final ERD.

Your ERD must be free of errors to receive full points. Hint: ER Assistant provides automated checks to ensure the ERD is error-free using the ‘Check Diagram’ function.

The correct answer and explanation is :

Creating an ER (Entity-Relationship) diagram with the specified requirements involves carefully considering entities, their attributes, and the relationships between them. Here’s a step-by-step guide and explanation for creating an ERD based on your requirements.

Step 1: Define Entities and Attributes

Let’s define five entities and their attributes:

1. Customer

• Attributes:
  • Customer_ID (Primary Key)
  • Name
  • Email
  • Phone_Number
  • Address
• Purpose: Represents a customer who purchases products. The attributes fully describe a customer, including their contact details and unique identifier.

1. Order

• Attributes:
  • Order_ID (Primary Key)
  • Order_Date
  • Total_Amount
  • Customer_ID (Foreign Key)
  • Payment_Method
• Purpose: Represents a customer’s order. The Customer_ID is a foreign key linking the order to the customer who placed it.

1. Product

• Attributes:
  • Product_ID (Primary Key)
  • Name
  • Description
  • Price
  • Stock_Quantity
• Purpose: Represents products available for sale. The attributes detail the product’s information and availability.

1. Order_Item

• Attributes:
  • Order_Item_ID (Primary Key)
  • Order_ID (Foreign Key)
  • Product_ID (Foreign Key)
  • Quantity
  • Unit_Price
• Purpose: Represents a specific product in an order. It links products to the order through the Order_ID and Product_ID.

1. Supplier

• Attributes:
  • Supplier_ID (Primary Key)
  • Name
  • Contact_Info
  • Address
  • Product_ID (Foreign Key)
• Purpose: Represents suppliers who provide products. The Product_ID links the supplier to a specific product they provide.

Step 2: Define Relationships and Cardinality

1. Customer and Order

• Relationship: A customer can place many orders, but each order is placed by only one customer.
• Cardinality: 1\:M (One customer to many orders)
• Optional/Mandatory: The relationship is mandatory from the Order side (every order must be linked to a customer) and optional from the Customer side (a customer may not have placed an order yet).

1. Order and Order_Item

• Relationship: An order can contain many order items, but each order item belongs to one order.
• Cardinality: 1\:M (One order to many order items)
• Optional/Mandatory: This is mandatory from the Order_Item side (every order item must belong to an order) and optional from the Order side (an order may not contain items yet).

1. Product and Order_Item

• Relationship: A product can be in many order items, and each order item corresponds to a specific product.
• Cardinality: 1\:M (One product to many order items)
• Optional/Mandatory: This relationship is mandatory from the Order_Item side (each order item must reference a product) and optional from the Product side (a product might not yet have been ordered).

1. Supplier and Product

• Relationship: A supplier can supply many products, but each product is supplied by one supplier.
• Cardinality: 1\:M (One supplier to many products)
• Optional/Mandatory: This relationship is mandatory from the Product side (each product must have a supplier) and optional from the Supplier side (a supplier might not yet be supplying any products).

Step 3: Create the ERD

You can create this ERD using ER Assistant or Visio. Follow these steps:

• ER Assistant:

1. Start with creating the entities and adding the attributes.
2. Define the primary keys and foreign keys.
3. Establish relationships between the entities by defining cardinality and whether they are mandatory or optional.
4. Use Crow’s Feet notation for relationships.

• Visio:

1. Use the “Crow’s Feet” database notation template.
2. Define the entities and attributes.
3. Link the entities with relationships, specifying cardinality.
4. Add comments for each entity and relationship to explain the business rules.

Step 4: Add Comments

• For each entity, add comments to explain the business rules, such as:
• Customer: “Represents individuals who purchase products. A customer can place multiple orders.”
• Order: “Represents customer purchases. Each order is tied to a single customer.”
• Order_Item: “Represents items in an order. Links a product to a specific order.”
• Product: “Represents products available for sale.”
• Supplier: “Represents suppliers who provide products to the company.”

Explanation (300 words)

An ER diagram models the relationships between entities in a system and provides a visual representation of how different elements interact with one another. In this scenario, we modeled a retail system where a Customer can place an Order. Each Order consists of multiple Order_Items, each referencing a Product. A Supplier provides these products, making the Supplier entity critical for understanding the flow of products in the system.

The business rules and cardinalities define how these entities relate to each other:

• A Customer can place multiple Orders, but each Order is linked to only one customer (1\:M cardinality). This makes the relationship between Customer and Order mandatory from the Order side.
• Order_Item connects Order and Product, reflecting that each order can contain multiple items and each item corresponds to a specific product. This ensures products are tracked within each order, while also allowing a product to be included in multiple orders.
• The Product and Supplier relationship shows that a supplier can provide multiple products, but each product is supplied by one supplier. This is essential for managing inventory and product sourcing.

The attributes of each entity fully describe their role in the system, ensuring clarity in both the ERD and the underlying business process. Comments embedded in the ERD provide further context for how each entity operates and how they interact with others, making the diagram a comprehensive tool for database design and system analysis.