MongoDB Basics

Level : Beginner
Mentor: Shailendra Chauhan
Duration : 00:02:00

Database in MongoDB

A database in MongoDB refers to a group of collections. A single MongoDB instance can include many databases, each grouping zero or more collections. Every database has its permissions, often kept in a separate file on a disc.

What is RDBMS?

RDBMS refers to Relational Database Management Systems. It is the most popular database. It stores data in the form of rows, which are tuples. It has several tables, and the data is easily accessible because it is stored in the table. 

Documents in MongoDB

The document is essentially the heart of MongoDB. In simple terms, the document is an ordered collection of keys with related values. It is equivalent to table rows in relational database management systems. It always maintains a dynamic scheme and does not require any predefined structure or fields.

Collection in MongoDB

A collection is a grouping of documents. The collection mostly represents the table objects in RDBMS systems.

Dynamic Schema

Collections in MongoDB have dynamic schemas by default. Dynamic Schemas refer to that the documents in a single collection may have multiple forms of structure or shapes.

MongoDB: Hierarchical Objects

MongoDB's hierarchical objects refer to its document-oriented structure, in which data is stored as flexible, JSON-style documents. These documents can include nested fields and arrays, allowing for the representation of complicated data structures in a single record.

Built-In Databases in MongoDB

Built-in databases are essential to MongoDB's operation and include:

  • admin: This database handles administrative activities and access control, like user authentication and cluster administration.
  • local: Used for internal operations, specifically replica set syncing and temporary data storage during the replication process.
  • config: This database stores sharding-related metadata in a MongoDB sharded cluster, such as data distribution among shards.

User Defined Database in MongoDB

Users can create custom databases in MongoDB as needed. These user-defined databases are established implicitly when data is placed into a non-existing database, or directly using commands like use <database_name>. Each user-defined database runs independently, allowing for data separation and isolation of concerns in the MongoDB environment.

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