Mongo DB is document based No SQL database.

Advantange of Mongo DB

1. Clear structure of object
2. Less Schema
3. No complex query and query join
4. Easy to scale
5. Faster to store and access data.

Download & Install Mongo DB Community edition for windows

Download link:

Install .msi Installer

Install

1. Run Mongo DB installer
2. Install Mongod as service

Check mongodb version

mongo --version

Starting Mongo DB(Open terminal or Window DOS, Shell)

mongod

Use Mongo DB shell

mongo

Choose or create new database

Syntax:

use database_name

Example:

use capscom

To check current database

db

Show all databases

show dbs

Drop database

db.dropDatabase()

Create collection(Like table)

db.createCollection(collection_name)

Show created collections

show collections

Drop collection

db.collection_name.drop()

CRUD implementation in Mongo DB

Create or Insert records

Retrieve or fetch records

Update record

db.collection_name.updateOne({field_name: value}, {$set: {field_name: value}})

db.collection_name.updateMany({field_name: value}, {$set: {field_name: value}})

Remove records

db.collection_name.remove(condition, FLAG) // FLAG can be 1 or true
// One is declaring only one record will delete at a time

Remove all records

db.collection_name.remove({});

Remove a single record

db.collection_name.remove({country: 'India', 1})

Remove all matched records

db.collection_name.remove({country: 'India'})

Where clause with operators

db.collection_name.find({field_name: {$gt: value } } )

db.collection_name.find({field_name: {$gte: value } } )

db.collection_name.find({field_name: {$lt: value } } )

db.collection_name.find({field_name: {$lte: value } } )

db.collection_name.find({field_name: {$ne: value } } )

db.collection_name.find({field_name: {$in: [item1, item2] } } )

db.collection_name.find({field_name: {$nin: [item1, item2] } } )

db.collection_name.find( $and: [ {field_name: value}, {field_name: value} ] )

db.collection_name.find( $or: [ {field_name: value}, {field_name: value} ] )

db.collection_name.find( { field_name : {$not: { $operator: value } } } )
Ex: db.products.find( { price: {$not: { $gt: 200 } } } )

Example

db.products.find({'qty': {$gt: 10}});

// will retrieve all products that have qty greater than 10

Limit & Skip documents in mongodb

db.collection_name.find().limit(n).skip(m)

// where n is how many document will fetch and m is how many document will skip.

Fetch documents in ascending or descending order

Fetch records in ascending order

db.collection_name.find().sort({field_name: 1})

Fetch records in descending order

db.collection_name.find().sort({field_name: -1})

Mongoose An ODM(Object Data Modeling) for mongodb

Install mongoose using npm

npm install mongoose

Load mongoose on application

let mongoose= require('mongoose')

Create a connection

mongoose.connect('mongodb://localhost:27017/database_name')

Note: localhost can be replaced with 127.0.0.1

check mongoose connection status

mongoose.connection.on('connected', function(){
  console.log('Connected with mongodb');
})

Create Schema for document models

Consider you have document users to store user information, so first of all we will create schema for users document which will be skelton of document.

Load Schema from mongoose

cons {Schema} = mongoose

Create user schema

let UserSchema=new Schema({
 username: String,
 email: String,
 password: String
});

Create Model

const UserModel= mongoose.model('users', UserSchema);

CRUD Operations on mongoose.

await UserModel.create({
 username: 'capscom', 
 email:'capscomtech@gmail.com', 
 password: '12345'
});

let users= UserModel.find({});

await UserModel.updateOne({ id: id_value },  {
    username: req.body.username,
    email: req.body.email,
    password: req.body.password
  });

let deletedUser=UserModel.findByIdAndDelete(id, (error)=>{
     if(error) throw error;
     console.log("user deleted");
  })