What is a relational database?

A relational database (RDB) is a database management system that stores data in the form of tables (relations). Each table consists of rows (records) and columns (attributes), where each row is uniquely identified by a primary key.

Main characteristics of relational databases:

• Data is structured into tables with clearly defined relationships between them (via foreign keys).
• SQL language is used for defining, manipulating, and querying data.
• Data integrity is maintained through constraints (e.g., uniqueness, references).
• Transactional processing with ACID properties (atomicity, consistency, isolation, durability) is supported.

Example: a users table with columns id, name, email, where id is the primary key, and another orders table with a foreign key referencing the user id.