MongoDB - Official website - Source code - Document - Download address - Score()

MongoDB is an open source, non-relational (NoSQL) database based on distributed file storage. Written in C++. It is the richest and most like a relational database among non-relational databases. It supports very loosely structured data, which is similar to json's bson format and can store more complex Data types. MongoDB supports a very powerful query language whose syntax is a bit like an object-oriented query language, which can perform almost all functions like relational database form queries, and also supports indexing data.

CouchDB - Official website - Source code - Document - Download address - Score()

Apache CouchDB is a document-oriented database management system. It provides a RESTful interface with JSON as the Data format to manipulate it and manipulate the organization and presentation of documents through views. CouchDB is the top open source project for the Apache Foundation.

CouchBase - Official website - Source code - Document - Download address - Score()

CouchBase is an open source, distributed, document-oriented NOSQL database that is primarily used in the field of distributed caching and Data storage. It is built by combining the functional features of Apache CouchDB and MemBase databases. MemBase is based on Memcached. CouchBase therefore combines the simplicity, reliability of CouchDB with the high performance and scalability of Memcached.