What is the difference between a primary key and a foreign key in a database?

The Difference Between Primary Key and Foreign Key in a Database

When it comes to database management, understanding the distinction between a primary key and a foreign key is essential. Both primary keys and foreign keys play a crucial role in maintaining data integrity within a database.

Primary Key

A primary key is a unique identifier for each record in a database table. It serves as a unique reference point for each row and ensures that each entry is distinct. The primary key enforces entity integrity by preventing duplicate or null values in the designated column. In most databases, the primary key is automatically indexed for faster query performance.

Foreign Key

A foreign key, on the other hand, establishes a relationship between two tables in a relational database. It is a field (or a combination of fields) in one table that matches the primary key in another table. This relationship allows data to be linked and maintained across multiple tables, ensuring referential integrity. Foreign keys help maintain data consistency by enforcing constraints on the values that can be inserted into the foreign key column.

In summary, a primary key uniquely identifies each record in a table, while a foreign key establishes relationships between tables by linking to the primary key of another table.

Understanding the difference between primary keys and foreign keys is crucial for effective database design and management.