MongoDB Overview

         MongoDB is an open-source document database, and leading NoSQL database. MongoDB is written in c++.


               MongoDB is a cross-platform, document oriented database that provides, high performance, high availability,   and easy scalability.

                MongoDB works on concept of collection and document.

Database

Database is a physical container for collections. Each database gets its own set of files on the file system. A single
MongoDB server typically has multiple databases.

Collection

Collection is a group of MongoDB documents. It is the equivalent of an RDBMS table. A collection exists within a
single database. Collections do not enforce a schema. Documents within a collection can have different fields.
Typically, all documents in a collection are of similar or related purpose.

Document

A document is a set of key-value pairs. Documents have dynamic schema. Dynamic schema means that documents
in the same collection do not need to have the same set of fields or structure, and common fields in a collection's
documents may hold different types of data.

 Relationship of RDBMS terminology with MongoDB

RDBMS    MongoDB
Database        Database
Table              Collection
Tuple/Row     Document
column           Field
Table Join       Embedded Documents
Primary Key   Primary Key (Default key _id provided by mongodb   itself)
Database Server and Client
Mysqld/Oracle       mongod
mysql/sqlplus          mongo