Week 1 - Understanding Relational Databases

Which of the following is an example of an attribute for a 'Student' entity in a school database?

• School Name

• Student ID

• Teacher Name

• Class Schedule

Answer explanation

The 'Student ID' is a unique identifier for each student, making it a key attribute of the 'Student' entity. In contrast, 'School Name', 'Teacher Name', and 'Class Schedule' pertain to other entities or aspects of the school.

In a database representing a library system, which of the following is an example of an entity?

• Author's Name

• Book Title

• Book Publication Date

• Author

Answer explanation

In a library database, an entity represents a distinct object or concept. 'Author' is an entity as it refers to a person who writes books, while 'Author's Name', 'Book Title', and 'Book Publication Date' are attributes of entities.

Identify based on the scenario below, what kind of entity relationship it belongs to: Each student has a unique personal residential address. What kind of relationship should the student and the address be defined as?

• One-to-One relationship

• One-to-Many relationship

• Many-to-Many relationship

• None-to-One relationship

Answer explanation

The relationship between a student and their unique residential address is a One-to-One relationship, as each student is associated with exactly one address, and each address corresponds to only one student.

Identify based on the scenario below, what kind of entity relationship it belongs to: A Book can have one or more authors. An Author can write multiple books.

• One-to-One

• One-to-Many

• Many-to-Many

Answer explanation

The relationship is Many-to-Many because a Book can have multiple Authors, and an Author can write multiple Books. This mutual association indicates that each entity can relate to many instances of the other.

Identify based on the scenario below, what kind of entity relationship it belongs to: An Order can include multiple food items. A Food Item can be added to different orders.

• One-to-One

• One-to-Many

• Many-to-Many

Answer explanation

The relationship is Many-to-Many because an Order can contain multiple Food Items, and a Food Item can be part of different Orders. This mutual inclusion indicates a Many-to-Many relationship.

Identify based on the scenario below, what kind of entity relationship it belongs to: A Team can have multiple players. One Player can only be in one team.

• One-to-One

• One-to-Many

• Many-to-Many

Answer explanation

The scenario describes a relationship where one Team can have multiple Players, but each Player belongs to only one Team. This defines a One-to-Many relationship, as one entity (Team) relates to many entities (Players).

Which of the following best describes a primary key?

• A key used to secure data encryption

• A key used to sort the data in ascending order

• A unique identifier for each record in a table

• Used to ensure reference integrity

Answer explanation

A primary key is a unique identifier for each record in a table, ensuring that no two records have the same key. This is essential for maintaining data integrity and enabling efficient data retrieval.

Which statement is TRUE of primary and foreign keys?

• A primary key uniquely identifies each record in a table.

• A foreign key must have the same name as a primary key it references

• A primary key can have duplicate values within a table

• A foreign key must always reference a primary key in the same table.

Answer explanation

A primary key uniquely identifies each record in a table, ensuring no duplicates. The other statements are incorrect: foreign keys can have different names, primary keys cannot have duplicates, and foreign keys can reference primary keys in different tables.

Which statement is TRUE regarding attributes in a database?

• Attributes can exist independently of entities.

• Attributes are used to define the characteristics of an entity.

• An attribute can contain multiple entities.

• Attributes are the primary keys of the database.

Answer explanation

The correct statement is that attributes are used to define the characteristics of an entity. They provide specific details about the entity, such as its properties, which is essential for database organization.

Which of the following statements correctly identifies the difference between an entity and an attribute?

• Entities are unique identifiers; attributes are descriptive elements.

• Entities represent real-world objects; attributes are qualities of those objects.

• Entities are always numerical; attributes are always textual.

• Entities cannot have attributes.

Answer explanation

The correct choice states that entities represent real-world objects, while attributes describe the qualities of those objects. This distinction is fundamental in data modeling, where entities are the items of interest and attributes provide details about them.