A Level Computer Science OCR Practice Exam

What is the primary requirement for a relation to be in Third Normal Form (3NF)?

1. All attributes must be dependent on the primary key

2. No repeating groups in the table

3. All attributes not reliant on another non-key attribute

4. All data fields must be atomic

The correct answer is: All attributes not reliant on another non-key attribute

To meet the requirements for a relation to be in Third Normal Form (3NF), the correct condition is that all attributes must be dependent only on the primary key and not on any other non-key attributes. This means that any attribute in a table should be a function of the primary key, ensuring that there are no transitive dependencies present. A transitive dependency occurs when a non-key attribute depends on another non-key attribute, which can lead to redundancy and anomalies in the database. For instance, if you have a database of students in which the class details are stored alongside student details, the instructor's name should not be dependent on the class ID, as this could lead to problems if the instructor for that class changes. In 3NF, each piece of data should directly relate to the primary key alone, promoting data integrity and reducing redundancy. The other options refer to different aspects of database normalization. Ensuring all attributes are dependent on the primary key is crucial but not sufficient alone for 3NF. The absence of repeating groups pertains more to First Normal Form (1NF), while ensuring datatypes are atomic (meaning indivisible) aligns with 1NF as well. Thus, the focus on dependencies related solely to non-key attributes is what firmly