What does an RDBMS consist of?

A foreign key is a column (or a set of columns) in one table that refers to the primary key of another table. It establishes a link between the two tables, ensuring data consistency and integrity.  

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Imagine this:

You have a table called "Customers" with columns like "Customer ID", "Name", "Address".

You have another table called "Orders" with columns like "Order ID", "Customer ID", "Order Date", "Total Amount".

The "Customer ID" in the "Orders" table is a foreign key. It references the "Customer ID" in the "Customers" table. This means that every order must be associated with an existing customer.

Key points about foreign keys:

It maintains referential integrity, ensuring that related data exists.

It helps to normalize data by reducing redundancy.

It allows you to retrieve related data efficiently through joins.

By using foreign keys, you create a structured and connected database where information can be easily managed and retrieved.