What is a primary key in a database?

A primary key serves as a unique identifier for each record within a table in a database. This ensures that no two records can have the same value in the primary key field, enabling effective organization and retrieval of data. The importance of a primary key lies in its ability to uniquely distinguish records, which is crucial for maintaining data integrity.

In relational databases, the primary key is used to create and enforce relationships between tables, allowing for efficient data management and retrieval. This concept is foundational in database design because it underpins the relational model, ensuring that each entity (or record) can be referenced distinctly.

The other options describe characteristics that are not aligned with the definition of a primary key. A field that allows duplicates does not enforce uniqueness, which is critical for a primary key. A reference to an attribute in another table describes a foreign key, which serves a different purpose in establishing relationships between tables. Lastly, a field that stores timestamps is related to temporal data but has no bearing on the uniqueness or identification of records, which is the primary role of a primary key.