Question

A college or university will keep track of several addresses for a student, but each of these can be named differently: for example, consider that a student has a mailing address and a home address. Create an ERD for a student entity type with two composite attributes for student addresses where each comprises several single-valued attributes.

Short answer

The Entity-Relationship Diagram can be drawn as follows: The 'Student' entity is connected to the 'Has' relationship. The 'Has' relationship then connects to two composite attributes: 'Home Address' and 'Mailing Address'. Each composite attribute is further divided into smaller single-valued attributes, effectively illustrating the structure and relationships of the data.

Step-by-step solution

Identify Entities

First, identify the main entities that exist within the problem. The primary entity in this case is 'Student'.

Identify Relationships

Next, identify the relationships that link the entities together. Every 'Student' has multiple 'Addresses', hence the relationship that is established is 'Has'

Define Composite Attributes

The 'Student' entity has composite attributes for different addresses i.e. 'Home Address' and 'Mailing Address'. Each of these composite attributes can be broken down into single-valued attributes. For instance, both 'Home Address' and 'Mailing Address' can be divided into sub-attributes like 'Street', 'City', 'State', and 'ZIP Code'.

Draw the ERD

Draw the 'Student' entity as a rectangle. Label the relationship 'Has' as a diamond and connect it to the 'Student' entity with a line. Then, illustrate the composite attributes ('Home Address' and 'Mailing Address') as ovals and connect them to the 'Has' relationship. Lastly, draw the single-valued attributes as smaller ovals connected to their relevant composite attribute.

Key concepts

Composite Attributes in ERD

When creating an Entity-Relationship Diagram (ERD), a clear understanding of composite attributes is crucial. Composite attributes refer to broader data fields that can be divided into smaller, more specific attributes. For instance, an address is a classic example of a composite attribute because it consists of several components such as street, city, state, and ZIP code.
This concept allows for structured data representation, making it easier to organize and access detailed information. When designing an ERD, composite attributes are illustrated as ovals connected to the main entity. Within each composite attribute oval, smaller ovals represent its sub-components. This visual representation ensures each part of the composite attribute is accounted for effectively.

• Composite attributes enhance clarity within an ERD.
• They provide a breakdown of complex data items into manageable pieces.

By decomposing attributes into finer details, one can facilitate better data retrieval and manipulation within a database.

Understanding the 'Student Entity'

In an ERD depicting a university or college database, a 'Student' entity represents a real-world student. This entity is crucial as it stores all pertinent information about the student needed by the institution. The 'Student' entity is typically depicted as a rectangle in an ERD.
Key relationships must be identified for the 'Student' entity. In this scenario, the primary relationship is between a student and their addresses. This relationship is often labeled 'Has' or something similar, denoting ownership or association.

• A 'Student Entity' might include attributes such as student ID, name, DOB, and more.
• It often serves as the primary or central entity in the ERD for educational databases.

By identifying and defining this entity first, you establish a solid foundation for constructing the rest of your ERD.

Address Attributes in a Student ERD

Address attributes play a significant role in detailing a student's information. Within the context of a 'Student' entity in an ERD, addresses can be complex, requiring various sub-attributes to fully represent them.
In the provided solution, each address is treated as a composite attribute. This means a student can have multiple named addresses, like 'Home Address' or 'Mailing Address'. For each type of address, the component attributes generally include:

• Street: The specific street address, often including the number and street name.
• City: The city in which the address is located.
• State: The state or region.
• ZIP Code: A postal code for mailing purposes.

These details allow the ERD to store and relay precise location information for students, which is essential for tasks like correspondence or defining residency.