Part 7: Connecting to a Database with Node.js

#node #mongodb #database

In the previous part of our Node.js series, we introduced Express.js, a powerful web application framework that simplifies server-side development. Now, let's take a significant step forward by integrating a database into our application. Databases are crucial for storing and retrieving persistent data. In this part, we'll explore how to connect to both SQL and NoSQL databases using Node.js.

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Overview of Databases

There are two primary types of databases commonly used with Node.js:

SQL Databases: These include relational databases like MySQL, PostgreSQL, and SQLite. They use structured query language (SQL) for defining and manipulating data.
NoSQL Databases: These include document-oriented databases like MongoDB. They provide flexible schemas and scale horizontally.

We'll cover examples of connecting to both a SQL and a NoSQL database.

Connecting to a SQL Database (MySQL)

Step 1: Install MySQL and Node.js Packages

First, ensure you have MySQL installed on your system. You can download it from the official MySQL website.

Next, install the mysql2 package in your Node.js project:

npm install mysql2

Step 2: Create a MySQL Database and Table

CREATE DATABASE nodejs_demo;
USE nodejs_demo;

CREATE TABLE users (
  id INT AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(255) NOT NULL,
  email VARCHAR(255) NOT NULL UNIQUE
);

Step 3: Connect to MySQL from Node.js

Create a file named database.js and add the following code to connect to your MySQL database:

database.js

const mysql = require('mysql2');

const connection = mysql.createConnection({
  host: 'localhost',
  user: 'root',
  password: 'your_password',
  database: 'nodejs_demo'
});

connection.connect(err => {
  if (err) {
    console.error('Error connecting to MySQL:', err.stack);
    return;
  }
  console.log('Connected to MySQL as ID', connection.threadId);
});

module.exports = connection;

Step 4: Interacting with the Database

Now, let’s add some code to interact with the database. Create a file named app.js and use the following code to insert and retrieve data:

app.js

const express = require('express');
const connection = require('./database');

const app = express();

app.use(express.json());

// Insert a new user
app.post('/users', (req, res) => {
  const { name, email } = req.body;
  connection.query('INSERT INTO users (name, email) VALUES (?, ?)', [name, email], (err, results) => {
    if (err) {
      return res.status(500).send(err);
    }
    res.status(201).send({ id: results.insertId, name, email });
  });
});

// Get all users
app.get('/users', (req, res) => {
  connection.query('SELECT * FROM users', (err, results) => {
    if (err) {
      return res.status(500).send(err);
    }
    res.send(results);
  });
});

const PORT = 3000;
app.listen(PORT, () => {
  console.log(`Server running at http://localhost:${PORT}/`);
});

Connecting to a NoSQL Database (MongoDB)

Step 1: Install MongoDB and Node.js Packages

Ensure MongoDB is installed on your system. You can download it from the official MongoDB website.

Next, install the mongoose package in your Node.js project:

npm install mongoose

Step 2: Connect to MongoDB from Node.js

Create a file named database.js and add the following code to connect to your MongoDB database:

database.js

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost:27017/nodejs_demo', {
  useNewUrlParser: true,
  useUnifiedTopology: true
});

const db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', () => {
  console.log('Connected to MongoDB');
});

module.exports = mongoose;

Step 3: Define a Mongoose Schema and Model

Create a file named userModel.js and define a schema and model for users:

userModel.js

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
  name: String,
  email: { type: String, unique: true }
});

const User = mongoose.model('User', userSchema);

module.exports = User;

Step 4: Interacting with the Database

Use the following code in app.js to insert and retrieve data from MongoDB:

app.js

const express = require('express');
const mongoose = require('./database');
const User = require('./userModel');

const app = express();

app.use(express.json());

// Insert a new user
app.post('/users', async (req, res) => {
  try {
    const user = new User(req.body);
    await user.save();
    res.status(201).send(user);
  } catch (err) {
    res.status(400).send(err);
  }
});

// Get all users
app.get('/users', async (req, res) => {
  try {
    const users = await User.find();
    res.send(users);
  } catch (err) {
    res.status(500).send(err);
  }
});

const PORT = 3000;
app.listen(PORT, () => {
  console.log(`Server running at http://localhost:${PORT}/`);
});

Conclusion

Integrating databases with your Node.js applications allows you to manage and persist data efficiently. Whether using SQL databases like MySQL or NoSQL databases like MongoDB, Node.js provides powerful tools and libraries to facilitate database operations. In the next part of our series, we’ll explore authentication and authorization, essential for securing your applications.

Stay tuned for more advanced Node.js development techniques!

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