MongoDB

MongoDB is a document database which belongs to a family of databases called NoSQL - not only SQL. In MongoDB, records are documents which behave a lot like JSON objects in JavaScript. Values in documents can be looked up by their field’s key. Documents can have some fields/keys and not others, which makes Mongo extremely flexible.

Features	Relational (SQL)	Non-Relational (NoSQL)
Data Type	Hard to store rich data type	Able to store literally any type of data
Scaling	Not trivial to scale, and not cheap	Scaling is automatic and transparent
Cost	Expensive to build and maintain	Around 10% cost to Relational DB
Representation	Represents data in tables and rows	Represents data as collections of JSON documents
Query	Structured Query Language (SQL): makes SQL injection attack possible	Object Querying: intuitive, passing a document to explain what you're querying for
Multi-originated	JOIN operation: perform query across multiple tables	Multi-dimensional data type: support array and even other documents
Atomic Style	Support Atomic Transaction: able to contain multiple operations with a transaction and roll back the whole thing if it were a single operation	Does not support Atomic Transaction, but single operations are atomic
Schema	Require to define tables and columns before storing. Each row has same columns	No schema, drops in documents. Two documents in a collection can have different fields
Perfomance	Poor performance when using ORM	Perform much better
Application	Better when: Data structure fits nicely into table and rows. Or Require SQL or transactions	Better when: Data seems complex in relational database system. Or De-normalizing database schema or coding around performance. Or Can not pre-define schema or want to store records in same collection that have different fields

This is different than SQL databases like MySQL and PostgreSQL, where fields correspond to columns in a table and individual records correspond to rows.

5Steps to Run:

1.Download MongoDB

2.Extract the Path

3. Go as Cmd as Following Path :-   cd Downloads/mongodb-osx-x86_64-4.0.2/bin/

4. Run :  iMac:bin Santosh_imac$ mongod

2018-09-19T11:12:24.339+0530 I CONTROL  [main] Automatically disabling TLS 1.0, to force-enable TLS 1.0 specify --sslDisabledProtocols 'none'

2018-09-19T11:12:24.491+0530 I CONTROL  [initandlisten] MongoDB starting : pid=26402 port=27017 ...................................................................................................................

5.open another cmd Run in same path : bin santosh_imac$ mongo

MongoDB shell version v4.0.2

connecting to: mongodb://127.0.0.1:27017

MongoDB server version: 4.0.2

Server has startup warnings: 

2018-09-19T11:12:35.781+0530 I CONTRO

6.  > show dbs

=============================================================================================

7. Show Collections

8. db.collectionname.find()

9.db.createnamecollection.save({"name":"xyz"})