Relational Database Fundamentals & ERDs

In a relational database, what best describes an entity?

• A numeric field used for calculations only

• A real-world object represented as a table

• A visual notation used for joins only

• A temporary cache layer for queries

Which statement correctly defines an attribute in a table?

• A relationship between two separate tables

• A characteristic of an entity stored as columns

• A runtime parameter for SQL procedures

• A visualization element inside an ERD diagram

An ERD shows relationships such as One-to-Many. Which scenario matches One-to-Many?

• One invoice referencing multiple customers

• Multiple customers for one invoice

• One customer with multiple invoices

• Multiple invoices referencing multiple databases

In the Invoice entity shown, customer_id(FK) most likely represents what?

• A computed column for invoice totals

• A primary key unique to each customer

• An index created for faster full scans

• A foreign key referencing the Customer table

Which column would most reasonably be the primary key of the Invoice table?

• A composite of all non-null columns

• invoice_nr uniquely identifying each invoice

• customer_id uniquely identifying each customer

• date uniquely identifying each record

What is the main purpose of relationships in a relational database?

• To define how entities interact by common fields

• To compress tables for better storage

• To store calculated values for analytics only

• To enforce display rules in ERD software

Which statement best describes a primary key in a relational table?

• A label stored outside the table

• A column used only for sorting

• A field that may repeat across rows

• A unique row identifier, never NULL

In a Student–Enrollments schema, which pair most appropriately forms a composite key for Enrollments?

• ClassID and GPA

• StudentID and ClassID

• Name and ClassRoom

• StudentID and Address

What is the primary role of a foreign key?

• Optimize query execution plans

• Encrypt sensitive attributes

• Generate random unique values

• Link to a primary key in another table

Which scenario illustrates an update anomaly?

• Storing the same data in multiple places

• Changing an address in one row but not another duplicate

• Deleting a class removes the only student record

• Unable to add a new student lacking ClassID