What is a primary key in a database?

What is a primary key in a database?

• A. A field that stores the date and time of record creation.
• B. A type of data encryption used for sensitive fields.
• C. A unique identifier for each record in a table.
• D. A method to back up the database.

Answer: (C)

A primary key is the unique fingerprint of a row in a table. It provides one clear identifier that distinguishes every record from all others, so you can locate, update, or relate a specific row without confusion. The values must be unique and not null, and it can be a single column or a combination of columns (a composite key). This unique, non-null identifier is what enables fast lookups and reliable links to related data in other tables through foreign keys. The other ideas described—storing a creation timestamp, encrypting sensitive fields, or backing up the database—serve different purposes and do not define a record’s unique identity.

A primary key is the unique fingerprint of a row in a table. It provides one clear identifier that distinguishes every record from all others, so you can locate, update, or relate a specific row without confusion. The values must be unique and not null, and it can be a single column or a combination of columns (a composite key). This unique, non-null identifier is what enables fast lookups and reliable links to related data in other tables through foreign keys. The other ideas described—storing a creation timestamp, encrypting sensitive fields, or backing up the database—serve different purposes and do not define a record’s unique identity.