A Level Computer Science OCR Practice Exam

What defines a secondary key in a database?

1. A key that is used for authentication

2. A key field which can be used to index the data in a different order

3. A field that automatically increments

4. A temporary placeholder for data

The correct answer is: A key field which can be used to index the data in a different order

A secondary key in a database is utilized to index data in a different order than the primary key. This allows for more flexible querying and sorting capabilities. While the primary key uniquely identifies a record, the secondary key can be a non-unique field that provides an alternative way to access and organize data based on different criteria. This is particularly useful for optimizing search performance, enabling users to retrieve records based on various attributes without primarily relying on the primary key. The other options do not accurately reflect the concept of a secondary key. A key for authentication pertains to security measures rather than data organization. An automatically incrementing field typically describes a primary key setup, where unique identifiers are generated sequentially. Lastly, a temporary placeholder is not related to key classification in databases and often references concepts like temporary variables or staging areas in programming, not database indexing.