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 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 is a group of MongoDB documents. It is the equivalent of an RDBMS table. A collection exists within a single database.
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.
| 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 |