What types of databases are you familiar with?

The following main types of databases are known:

• Relational (SQL): Organize data into tables with rows and columns. Relationships between tables are established through primary and foreign keys. Uses the structured query language SQL.

  • Examples: PostgreSQL, MySQL, Oracle Database, Microsoft SQL Server, SQLite.

• Non-relational (NoSQL): Designed to work with large volumes of unstructured or semi-structured data. No fixed schema. There are several subtypes:

  • Document-oriented: Store data as documents (e.g., JSON, BSON, XML).
    • Examples: MongoDB, Couchbase, CouchDB.
  • Key-value: Store data as key-value pairs. The simplest type.
    • Examples: Redis, Memcached, Amazon DynamoDB (in key-value mode).
  • Columnar: Store data by columns, optimizing reading data from specific columns.
    • Examples: Apache Cassandra, HBase, ClickHouse.
  • Graph: Designed for storing and processing data represented as graphs, where nodes represent entities and edges represent relationships.
    • Examples: Neo4j, ArangoDB (also has other models), OrientDB.

• Embedded: Databases that are integrated directly into an application. Usually less functional but faster and do not require separate installation and administration.

  • Examples: SQLite, H2 Database, Derby.

• In-memory: Store data entirely or partially in server RAM for very fast access.

  • Examples: Redis (mainly in-memory), Apache Ignite, SAP HANA.

• Time-series: Optimized for storing and analyzing data with timestamps.

  • Examples: InfluxDB, TimescaleDB (PostgreSQL extension).

Each type has its advantages and disadvantages, and the choice depends on specific project requirements: data volume and structure, scaling needs, access speed, and query types.