## Primary and Foreign Keys
In **relational databases**, the foundation lies in tables and their relationships, which are often established using **Primary Keys** and **Foreign Keys**.

- A **Primary Key (PK)** serves as a unique identifier for a record within a table.

- A **Foreign Key (FK)** references the **Primary Key** of a different table, connecting records between them.

Take, for instance, two tables: "**student**" and "**group**." In the "**student**" table, each record might have details such as **id** (representing the student's ID), **name**, **surname**, **age**, and **group_id** (which is a foreign key pointing to the primary key of the “**group**” table). The “**group**” table, on the other hand, might contain **id** (indicating the group's ID), **name**, and **grade**.

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From this, it's evident that both **John** and **Kesha** are members of the **BG1** group, as indicated by their foreign key referencing the **group id**. The **BG4** group has one student, **Emma**, while the **MG2** group currently has no students associated with it.

Such a structure facilitates the use of `JOIN` operations in database queries.

Take a closer look at the “**group-student**” entity-relationship (ER) diagram:

This section dives into the world of relational and non-relational databases, teaching you how to visually represent database structures.

We'll dive deep into relational databases, giving you a thorough understanding of essential concepts. This includes topics like foreign keys, various ON DELETE options, and the different types of relationships.

Ready to build a database? This section will hone your skills, emphasizing the importance of a well-structured database for peak performance. Here, you'll grasp the fundamental principles of crafting user-friendly databases.

Relational Database and Normalization

Structure. Primary Key and Foreign Key

Primary and Foreign Keys

What is a primary key?

What is a foreign key?