Introduction
MongoDB is the world’s leading NoSQL database server, and—per DBengine’s ranking, the most widely-known ranking in the database industry—the 5th database server overall in terms of popularity.
MongoDB is a document-oriented database server, using JSON-formatted documents for data rather than the columns and rows of the table structure known to any relational database administrator. This structure allows a flexibility that is difficult to obtain in current relational databases, and is behind the “schema-less” nature of MongoDB. A “collection”, as the MongoDB equivalent of a relational database table is known, does not impose a specific structure on its documents. Practically speaking, this means — among other benefits — that each document in the collection can have differing fields, and a field that exists in one document in the collection need not exist in another. The JSON format also brings embedded arrays, and the ability to index on any attribute among other features.