Mastering MongoDB Queries with Node.js: A Comprehensive Guide

This document provides a detailed introduction to using MongoDB with Node.js, focusing on how to perform various database queries. This guide is designed to help beginners understand key concepts and practical examples essential for working with these technologies.

Key Concepts

• Node.js: A JavaScript runtime built on Chrome's V8 engine that allows you to execute JavaScript on the server side.
• MongoDB: A NoSQL database that stores data in a flexible, JSON-like format called BSON (Binary JSON).
• MongoDB Driver: A library that enables Node.js applications to connect to and interact with MongoDB databases.

Setting Up

1. Install MongoDB: Ensure you have MongoDB installed and running on your machine.

Install MongoDB Driver: Use npm to install the MongoDB driver for Node.js:

npm install mongodb

Basic Operations

1. Connecting to MongoDB

To perform queries, you first need to connect to your MongoDB database. Here’s a simple example:

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

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

// Connect to the server
async function run() {
    await client.connect();
    console.log("Connected successfully to server");
    const database = client.db('mydatabase');
}

run().catch(console.dir);

2. Inserting Documents

You can insert documents (records) into a MongoDB collection using the insertOne or insertMany methods.

Example:

const collection = database.collection('mycollection');

// Insert a single document
const insertResult = await collection.insertOne({ name: "Alice", age: 25 });
console.log('Inserted documents:', insertResult.insertedId);

3. Querying Documents

You can query documents in a collection using methods like find and findOne.

Example:

// Find one document
const findResult = await collection.findOne({ name: "Alice" });
console.log('Found document:', findResult);

// Find multiple documents
const cursor = collection.find({ age: { $gt: 20 } });
await cursor.forEach(doc => console.log(doc));

4. Updating Documents

To update existing documents, use updateOne or updateMany.

Example:

const updateResult = await collection.updateOne({ name: "Alice" }, { $set: { age: 26 } });
console.log('Updated documents:', updateResult.modifiedCount);

5. Deleting Documents

You can delete documents using deleteOne or deleteMany.

Example:

const deleteResult = await collection.deleteOne({ name: "Alice" });
console.log('Deleted documents:', deleteResult.deletedCount);

Conclusion

This guide covers the foundational aspects of querying a MongoDB database using Node.js. By understanding how to connect to the database, insert data, and perform basic queries, beginners can start building applications that effectively utilize MongoDB.