What types of databases are there?

Main types of databases:

• Relational databases (SQL) — data is stored in tables with well-defined schemas. Examples: MySQL, PostgreSQL, Oracle.
• Document-oriented databases (NoSQL) — data is stored as documents (e.g., JSON). Example: MongoDB.
• Column-oriented databases — optimized for analytics and processing large volumes of data by columns. Example: Apache Cassandra.
• Graph databases — store data as nodes and relationships, suitable for social networks, recommendations. Example: Neo4j.
• Key-Value databases — simple structure where data is stored as key-value pairs. Example: Redis.

The choice depends on the task: relational for complex transactions, NoSQL for flexibility and scalability.