MongoDB Cheatsheet

MongoDB is a document-oriented NoSQL database that uses a BSON (Binary JSON) format to store data. It is highly scalable and flexible.

MongoDB Installation

Installation on Windows

Download the installer from the official page and follow the instructions.

Data Structure

Documents and Collections

• A document is an individual record, similar to a row in a relational database.
• A collection is a set of documents, comparable to a table.

{
  "_id": ObjectId("607d1c4e79b1f8d75e7ecf0b"),
  "name": "Juan",
  "age": 30,
  "city": "Madrid"
}

Connecting to MongoDB

Connect to the Database

Use the MongoDB shell to connect to a database:

mongo --host localhost --port 27017

Connection from Node.js

Install the MongoDB driver:

npm install mongodb

Connect from Your Application:

const { MongoClient } = require('mongodb');

const url = 'mongodb://localhost:27017';
const client = new MongoClient(url);

async function run() {
    try {
        await client.connect();
        console.log("Successfully connected to the database");
    } finally {
        await client.close();
    }
}

run().catch(console.dir);

CRUD Operations

Insert a Document

const result = await collection.insertOne({ name: "Juan", age: 30 });

console.log(`New document created with id: ${result.insertedId}`);

Insert Multiple Documents

const result = await collection.insertMany([
    { name: "Ana", age: 25 },
    { name: "Pedro", age: 35 }
]);
console.log(`${result.insertedCount} documents were inserted`);

Find a Document

const document = await collection.findOne({ name: "Juan" });
console.log(document);

Find Multiple Documents

const documents = await collection.find({ age: { $gt: 30 } }).toArray();
console.log(documents);

Update a Document

const result = await collection.updateOne(
    { name: "Juan" },
    { $set: { age: 31 } }
);
console.log(`${result.modifiedCount} document(s) updated`);

Update Multiple Documents

const result = await collection.updateMany(
    { age: { $lt: 30 } },
    { $set: { status: "young" } }
);
console.log(`${result.modifiedCount} document(s) updated`);

Delete a Document

const result = await collection.deleteOne({ name: "Juan" });
console.log(`${result.deletedCount} document(s) deleted`);

Delete Multiple Documents

const result = await collection.deleteMany({ age: { $lt: 30 } });
console.log(`${result.deletedCount} document(s) deleted`);

Advanced Operations

Aggregations

MongoDB allows for complex aggregation operations:

const results = await collection.aggregate([
    { $match: { age: { $gte: 25 } } },
    { $group: { _id: "$city", averageAge: { $avg: "$age" } } }
]).toArray();

console.log(results);

Indexes

Indexes improve query performance:

await collection.createIndex({ name: 1 });

List Indexes

const indexes = await collection.indexes();
console.log(indexes);

Filtering and Searching

Common Query Operators

Security and Authentication

User Authentication

You can create users and assign roles:

db.createUser({
  user: "user",
  pwd: "password",
  roles: [{ role: "readWrite", db: "myDatabase" }]
});

Connection with Authentication

const url = 'mongodb://user:password@localhost:27017/myDatabase';