How does a primary key in a database differ from a foreign key?

A primary key is a crucial concept in database management that serves as a unique identifier for each record within a table. It ensures that no two rows in the same table have the same key value, which is essential for maintaining data integrity. This uniqueness allows for efficient data retrieval and ensures that each record can be referenced unambiguously.

On the other hand, a foreign key is a field in one table that creates a link between that table and the primary key of another table. This relationship allows for the establishment of connections between different data sets in a relational database. By using foreign keys, databases can enforce referential integrity, ensuring that relationships between tables remain consistent.

The distinction between a primary key and a foreign key is vital for database normalization and the overall structure of the database. While the primary key is about ensuring the uniqueness of records within its own table, the foreign key's role is to link to records in different tables, providing a pathway for cross-referencing data across the database. Thus, understanding these roles aids in designing efficient and reliable database systems.