What is the purpose of a Primary Key (PK) in a table?

The primary key serves a crucial role in relational databases by uniquely identifying each record in a table. This uniqueness ensures that no two records can have the same primary key value, which is essential for maintaining data integrity and preventing duplication. With a primary key, it becomes possible to reliably reference specific records in queries and join operations. When designing a database, defining a primary key for each table helps organize data effectively and enforce rules about the entries made, allowing for straightforward retrieval and manipulation of data.

In contrast, while linking tables together is a function associated with the concept of foreign keys, it doesn't directly pertain to the primary key's primary purpose. Multiple entries contradict the uniqueness aspect of a primary key, and data models represent broader categories of database design rather than specifying the identity of individual records. Hence, the primary key is critical for uniquely identifying records in a table, which is its fundamental purpose in a relational database.