What’s New on the CPA ISC Exam in 2026:

This video is taken from an actual i75 ISC Course Video.   

The CPA ISC exam expects you to know relationships between tables in a database and be able to describe them as one-to one, one-to many, or many to many. The exam will also require you to know what a bridge table is, the purpose of a bridge table and when a bridge table is needed. 

A one-to-one (1:1) relationship in a database means:

Each record in Table A is linked to only one record in Table B, and each record in Table B is linked to only one record in Table A.

Core idea

It’s a one-to-exactly-one pairing between two tables.

Simple example (accounting context)

Suppose a company keeps:

Employee table

• EmployeeID
• Name
• HireDate

EmployeeBenefits table

• EmployeeID
• HealthPlan
• RetirementPlan

If:

• Each employee has exactly one benefits record, and
• Each benefits record belongs to exactly one employee,

→ That is a one-to-one relationship.

How it’s implemented

Usually:

• The primary key of one table is also a foreign key in the other table, or
• Both tables share the same unique ID.

Example:

• Employee.EmployeeID (PK)
• EmployeeBenefits.EmployeeID (PK and FK)

This enforces that no employee can have multiple benefits records and no benefits record can belong to multiple employees.

Why use a 1:1 relationship?

Common reasons:

• Data separation for security (e.g., payroll vs. general HR data)
• Logical organization
• Performance or access control

CPA-style takeaway

A 1:1 relationship is used when:

• Each entity instance corresponds to exactly one instance in another table
• Duplication and ambiguity must be avoided
• Sensitive data may need restricted access