What is NoSQL?

NoSQL (Not only SQL) is a type of database that stores data in a non-relational way. It is used to store data that does not fit into the traditional relational database model. NoSQL databases are often used in applications that require high scalability and flexibility, such as web applications, mobile applications, and real-time analytics.

The three most frequently used fields for NoSQL are:

1. Document databases: These databases store data in documents, which are collections of key-value pairs. Examples of document databases include MongoDB and CouchDB.
2. Graph databases: These databases store data in a graph structure, which is a network of nodes and edges. Examples of graph databases include Neo4j and OrientDB.
3. Column-oriented databases: These databases store data in columns, which are collections of related data. Examples of column-oriented databases include Cassandra and HBase.

In addition to the above, there are also other types of NoSQL databases such as key-value stores and wide-column stores.

In terms of technologies related to NoSQL, there are a number of open source projects and tools that can be used to manage NoSQL databases. These include Apache Hadoop, Apache Cassandra, MongoDB, and CouchDB. Additionally, there are a number of cloud-based NoSQL databases, such as Amazon DynamoDB and Google Cloud Datastore.