What is the difference between primary key and foreign key in databases?

A primary key is essential in a database as it uniquely identifies each record within a table. This means that no two rows can have the same value for the primary key, ensuring that each entry is distinct and can be identified without ambiguity. In contrast, a foreign key is used to establish a link between two tables. It is a column or a set of columns in one table that refers to the primary key in another table. This relationship helps maintain referential integrity, allowing for organized and related data across multiple tables.

By using a primary key and foreign key, databases can effectively manage relationships between different datasets. For instance, if you have a table of students with a primary key of student ID, and a table of courses where entries include a foreign key that references the student ID, it enables you to link each student to their enrolled courses. This ensures that the database can relate data efficiently and maintain accuracy.

The other choices do not accurately describe the roles or characteristics of primary and foreign keys within the context of databases. Understanding this fundamental concept is crucial for effectively designing and managing relational databases.