NoSQL (Not only SQL) is a paradigm in which the data is stored in the form of entities instead of the typical RDBMS type tabular relational format. One of the primary goals for NoSQL databases is horizontal scaling and high availability. Based on the underlying data structure of the NoSQL databases, they are categorized into:
- Document databases: Each key in the database is mapped to a document. A document can be a binary file or a nested structure like XML or JSON. The examples of document databases are MongoDB, CouchDB, Couchbase, and so on.
- Graph databases: These are useful with the data which is in the form of connected graphs like social media connections. The examples of graph databases are Neo4j, OrientDB, Apache Giraph, ...
