What types of databases are there?

Relational (SQL) and Non-Relational (NoSQL).

Relational Databases:

• Based on tables with predefined structure.
• Data is linked through keys.
• Use SQL for queries.
• Examples: MySQL, PostgreSQL, Oracle, SQL Server.

Non-Relational Databases:

• Do not have a fixed schema.
• Various data models: key-value, document-oriented, columnar, graph.
• More flexible for working with unstructured or semi-structured data.
• Often scale horizontally.
• Examples: MongoDB (document), Redis (key-value), Cassandra (columnar), Neo4j (graph).

The choice depends on the application's requirements for data structure, scalability, and consistency.