Mongoose

MongoDB Basics

# Show, create and switch to DB
 
show dbs
use dbname
show collections

// If no collection a new one is created on insertion of data
db.tours.insertOne({name: 'Hiking', price: 300, rating: 8})
db.tours.insertMany([{name: 'Hiking', price: 300, rating: 9}, {name: 'Trekking', price: 500, rating: 6}])
 
// Returns all document from the collection
db.tours.find()
db.tours.find({$or: [{price: {$lte: 300}}, {rating: {$gt: 6}}]})
 
// The second term is called as projection it is the fields that have to be in output
db.tours.find({$or: [{price: {$lte: 300}}, {rating: {$gt: 6}}]}, {name: 1})
db.tours.updateOne({name: 'Hiking'}, {$set: {price: 400}})
db.tours.updateMany({name: 'Hiking', rating: {$gt: 6}}, {$set: {premium: true}})
db.tours.replaceOne()
db.tours.deleteMany({rating: {$gte: 200}})
 
// Delete all the collections
db.tours.deleteMany({})

Initialize Module

const mongoose = require('mongoose');
 
mongoose
.connect('mongodb://localhost:27017/fruitsDB', {useNewUrlParser: true, useUnifiedTopology: true, useCreateIndex: true})
.then(() => console.log('Connected to DB');

Create Schema

// Schema for the Document Fruit
const fruitSchema = new mongoose.Schema({
	name: String,
	rating: Number,
	review: String
});

Field Validation

const fruitSchema = new mongoose.Schema({
	name: {
		type: String,
		required: ['true', 'Why no name ?'],
		unique: true
	},
	rating: {
		type: Number,
		default: 4.5,
		min: 1,
		max: 10
	},
	review: {
		type: String,
		required: true,
		select: false //Field will not show up in any output
	}
});

Creating Collection (Table)

// DB name is always converted to plural by mongoose
const Fruit = mongoose.model('Fruit', fruitSchema);

Create & Save Document (Row)

const apple = new Fruit({
	name: 'Apple',
	rating: 7,
	review: 'A apple a day keeps the doctor away!'
});
 
// Saves the created Document
apple.save();
 
// Automatically Saves the Document
const apple = Fruit.create({
	name: 'Apple',
	rating: 7,
	review: 'A apple a day keeps the doctor away!'
});
 
// Save multiple documents
Fruit.insertMany([apple, kiwi, orange, banana], function(err) {
	if(err) {
		console.log(err);
	}else {
		console.log('Successfully saved all the data');
	}
});

Select/ Fetch Document

Fetch subset of Records

Fruit.find({name: 'Apple'}, function(err, fruits) {
	if(err) {
		console.log(err);
	}else {
		console.log(fruits);
	}
});

Find Single Record

Fruit.findOne({name: 'Apple'}, function(err, fruit) {
	if(err) {
		console.log(err);
	}else {
		console.log(fruit);
	}
});

Find a document by ID

Fruit.findById(id, function(error, fruit){});

Update Document

Update a Document

Fruit.updateOne({name: 'Apple'}, {rating: 9}, function(err) {
	if(err) {
		console.log(err);
	}else {
		console.log('Successfully updated the data');
	}
});

NOTE

Can be used to add new fields to document as well but they should be specified in the schema. Refer document for other functions for updating

Update Document using ID field

Fruit.findByIdAndUpdate(id, {fields to update}, {new: true, runValidators: true}, function(err) {
	if(err) {
		console.log(err);
	}else {
		console.log('Successfully deleted the data');
	}
});

NOTE

The remove by id will only work if the callback is specified else it will only return the item with the id

Delete a Document

Delete Single Record

Fruit.deleteOne({name: 'Apple'}, function(err) {
 
	if(err) {
		console.log(err);
	}else {
		console.log('Successfully deleted the data');
	}
});

Delete all the data from DB

Fruit.deleteMany(function(err) {
	if(err) {
		console.log(err);
	}else {
		console.log('Successfully deleted the data');
	}
});

Delete using ID Field

Fruit.findByIdAndRemove(id, function(err) {
	if(err) {
		console.log(err);
	}else {
		console.log('Successfully deleted the data');
	}
});

NOTE

The remove by id will only work if the callback is specified else it will only return the item with the id

Relationship and Embedded Documents

const personSchema = new mongoose.Schema({
	name: String,
	age: Number,
	favouriteFruit: FruitSchema
});
 
const Person = mongoose.model('Person', personSchema);
 
const kiwi = new Fruit({
	name: 'Kiwi'
	rating: 10,
	review: 'An amazing fruit'
});
 
kiwi.save();
 
const david = new Person({
	name: David,
	age: 21,
	favouriteFruit: kiwi
});
 
david.save();

Close Connection

mongoose.connection.close();

Mongoose Methods

Fetch columns from Document

const fruit = Fruit.find().where('name').equals('Apple').where('rating').gte(6);

Pagination

const page = parseInt(req.query.page) || 1;
const limit = parseInt(req.query.limit)) || 100;
const skip = (page - 1) * limit;
 
Fruit.find().skip(skip).limit(limit);