An organized collection of structured information or data, typically stored electronically in a computer system.

There are many types, that you might don't know yet:

1. Relational Databases (RDBMS):
Organizing data into tables with relationships.

• Examples: MySQL, PostgreSQL, Oracle, SQL Server

2. NoSQL Databases:
Flexible, schema-less data storage for various data models.

• a. Document Databases (e.g., MongoDB, CouchDB)
• b. Key-Value Stores (e.g., Redis, DynamoDB)
• c. Wide-Column Stores (e.g., Cassandra, HBase)
• d. Graph Databases (e.g., Neo4j, Amazon Neptune)

3. Object-Oriented Databases:
Storing data as objects, mirroring object-oriented programming.

• Examples: ObjectDB, Versant

4. Hierarchical Databases:
Organizing data in a tree-like parent-child structure.

• Examples: IBM IMS

5. Network Databases:
Representing data as records connected by links.

• Examples: Integrated Data Store (IDS)

6. Time Series Databases:
Optimized for time-stamped or sequential data.

• Examples: InfluxDB, TimescaleDB

7. Spatial Databases:
Designed for storing and querying spatial data.

• Examples: PostGIS, Oracle Spatial

8. Multi-model Databases:
Supporting multiple data models within a single database system.

• Examples: ArangoDB, OrientDB

9. NewSQL Databases:
Combining SQL and NoSQL for scalability and consistency.

• Examples: Google Spanner, CockroachDB

10. In-Memory Databases:
Storing data in main memory for faster processing.

• Examples: Redis, Memcached

11. Distributed Databases:
Spreading data across multiple nodes for scalability and reliability.

• Examples: Apache Cassandra, Google Bigtable

12. Columnar Databases:
Storing data by column rather than by row for analytical queries.

• Examples: Apache Parquet, Google BigQuery

13. Data Warehouses:
Large-scale data storage optimized for analysis and reporting.

• Examples: Amazon Redshift, Snowflake

Among these, the two main types of databases that dominate the industry and cover the vast majority of use cases are: Relational & NoSQL!

These two categories represent the fundamental split in modern database technology. Relational databases have been the standard for decades, while NoSQL databases have gained significant popularity in the last decade or so, especially for handling large-scale, distributed, or unstructured data.

Let's jump right in and explore each type in detail.