What is a unique identifier within a row of a database called?

A unique identifier within a row of a database is called a primary key. The primary key serves several critical functions within the relational database model. It ensures that each record within a table can be uniquely identified, which is essential for maintaining data integrity and enabling efficient data retrieval. By enforcing uniqueness, the primary key prevents duplicate records, ensuring that the data remains reliable and can be accurately referenced.

The primary key can be a single attribute or a combination of multiple attributes, and it plays a vital role in establishing relationships between different tables in a database. It is often used in conjunction with foreign keys to create links between tables, facilitating data normalization and relational integrity.

In summary, the primary key is key to organizing data effectively within a relational database, allowing for quick lookups, maintaining uniqueness across records, and establishing relationships between tables.