MongoDB (from humongous) is a cross-platform document-oriented database. MongoDB eschews the traditional table-based relational database structure in JSON-like documents with dynamic schemas (MongoDB calls the format BSON), making the integration of data in certain types of applications easier and faster. Released under a combination of the GNU Affero General Public License and the Apache License, MongoDB is free and open-source software.

First developed by the software company MongoDB Inc. in October 2007 as a component of a planned platform as a service product, the company shifted to an open source development model in 2009, with MongoDB offering commercial support and other services. Since then, MongoDB has been adopted as backend software by a number of major websites and services, including Craigslist, eBay, and Foursquare among others. As of July 2015, MongoDB is the fourth most popular type of database management system, and the most popular for document stores.

Advantages of MongoDB over RDBMS

  • Schema less: MongoDB is document database in which one collection holds different different documents. Number of fields, content and size of the document can be differ from one document to another.
  • Structure of a single object is clear
  • No complex joins
  • Deep queryability: MongoDB supports dynamic queries on documents using a document based query language that's nearly as powerful as SQL
  • Tuning
  • Ease of scaleout: MongoDB is easy to scale
  • Conversion / mapping of application objects to database objects not needed
  • Uses internal memory for storing the (windowed) working set, enabling faster access of data

Where should use MongoDB?

  • Big Data
  • Content Management and Delivery
  • Mobile and Social Infrastructure
  • User Data Management
  • Data Hub

Does MongoDB support transactions?

MongoDB does not support multi-document transactions. However, MongoDB does provide atomic operations on a single document. Often these document-level atomic operations are sufficient to solve problems that would require ACID transactions in a relational database.

For example, in MongoDB, you can embed related data in nested arrays or nested documents within a single document and update the entire document in a single atomic operation. Relational databases might represent the same kind of data with multiple tables and rows, which would require transaction support to update the data atomically.

Does MongoDB support SQL?

No. However, MongoDB does support a rich query language of its own.