A Level Computer Science OCR Practice Exam

What distinguishes First Normal Form (1NF) from other normal forms?

1. It allows multiple values in a single field

2. Each tuple and attribute must hold only one value

3. It is not based on a primary key

4. It requires the presence of foreign keys

The correct answer is: Each tuple and attribute must hold only one value

First Normal Form (1NF) is primarily defined by the requirement that each column in a table should contain atomic, indivisible values, meaning that each field must hold only a single value. This characteristic is crucial because it ensures that the data is structured in a way that facilitates easier querying, manipulation, and avoidance of data redundancy. When a table conforms to 1NF, each record (or tuple) must represent a unique entity, and each attribute should only contain one piece of information at a time. For example, if a table lists students and their courses, rather than allowing a single field to hold multiple courses (like "Math, Science"), each course should be represented in its own row alongside the student. This foundational principle of 1NF distinguishes it from other normal forms, which incorporate additional rules regarding relationships between tables and dependencies, but all build upon the initial structure laid out by achieving 1NF. Other aspects, such as the requirements of foreign keys or the need for a primary key, come into play in later normal forms but are not defining characteristics of the first normal form itself.