How to Connect Node.js to MySQL: A Step-by-Step Guide

Node.js to MySQL- Node.js is a powerful JavaScript runtime that allows developers to build scalable and high-performance applications. One of the most common tasks you’ll encounter when developing web applications is connecting your Node.js app to a database. In this blog post, we will focus on connecting a Node.js application to a MySQL database. We’ll cover the installation of the necessary packages, setting up your database, and coding the connection.

Prerequisites to Connect Node.js to MySQL

Before we begin, you need to have the following:

1. Node.js: Make sure you have Node.js installed on your machine. You can download it from nodejs.org.
2. MySQL: You should have MySQL installed and running. If you don’t have it set up, you can download it from mysql.com.
3. Basic understanding of JavaScript and SQL.

Step 1: Install MySQL

If you haven’t already, install MySQL on your local machine or set up a remote MySQL database. Create a database and a user to interact with it:

CREATE DATABASE my_database;

CREATE USER 'my_user'@'localhost' IDENTIFIED BY 'my_password';

GRANT ALL PRIVILEGES ON my_database.* TO 'my_user'@'localhost';

FLUSH PRIVILEGES;

Step 2: Initialize Your Node.js Project

Create a new directory for your Node.js project and initialize it:

mkdir node-mysql-example
cd node-mysql-example
npm init -y

This will create a package.json file in your project directory.

Step 3: Install MySQL Package

To connect Node.js with MySQL, you can use the popular mysql package. Install it via npm:

npm install mysql

Step 4: Create a Connection to MySQL

Create a new JavaScript file named app.js in your project directory:

touch app.js

Open app.js in your favorite code editor and add the following code:

const mysql = require('mysql');

// Create a connection to the database
const connection = mysql.createConnection({
  host: 'localhost',
  user: 'my_user',        // your username
  password: 'my_password', // your password
  database: 'my_database'  // your database name
});

// Connect to the database
connection.connect((err) => {
  if (err) {
    console.error('Error connecting: ' + err.stack);
    return;
  }
  console.log('Connected as id ' + connection.threadId);
});

// Close the connection
connection.end();

Breakdown of the Code:

1. Import the mysql package using require.
2. Create a connection object using the details of your MySQL database (host, user, password, database).
3. Call the connect() method to establish the connection.
4. Log the thread ID of the connection or an error message if there is a problem.
5. Finally, close the connection with connection.end().

Step 5: Run Your Application

To test your connection, run the following command in your terminal:

node app.js

If everything goes well, you should see a message saying you are connected along with the connection ID.

Step 6: Querying the Database

Now that you have successfully connected to your MySQL database, you can execute queries. Let’s modify app.js to fetch and log some data from a sample table.

Assuming you have a table called users, you can add the following code before connection.end():

// Querying the database
const query = 'SELECT * FROM users';

connection.query(query, (err, results) => {
  if (err) {
    console.error('Error fetching data: ' + err.stack);
    return;
  }

  console.log(results);
});

Replace users with the name of the table you have in your my_database. When you run node app.js, it will log the retrieved data from the users table.

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Another Approach

Connecting a Node.js to MySQL database is a common task, and you can achieve it using various packages. One of the most popular packages is mysql2, which supports both callbacks and promises, making it easy to work with asynchronous code in Node.js.

Below is a step-by-step guide on how to connect Node.js to MySQL using the mysql2 package.

Step 1: Install MySQL and Required Packages

First, make sure you have MySQL installed on your machine. You can download it fromthe MySQL website.

Once MySQL is set up, you can create a new Node.js project and install mysql2 by running:

 npm init -y
npm install mysql2

Step 2: Create a Database and Table

You can use the MySQL command line or a GUI such as MySQL Workbench to create a database and a table. For example:

 CREATE DATABASE testDB;

USE testDB;

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(100),
    age INT
);

Step 3: Connect to Node.js to MySQL

Now you can write some Node.js code to connect to your MySQL database and perform some basic operations. Create a file named index.js and add the following code:

 // index.js
const mysql = require('mysql2');

// Create a connection to the database
const connection = mysql.createConnection({
    host: 'localhost',    // Replace with your host name
    user: 'root',         // Replace with your MySQL username
    password: '',         // Replace with your MySQL password
    database: 'testDB'    // Replace with your database name
});

// Connect to the database
connection.connect((err) => {
    if (err) {
        console.error('Error connecting to MySQL:', err);
    } else {
        console.log('Connected to MySQL database.');

        // Perform a query
        const sql = 'INSERT INTO users (name, age) VALUES (?, ?)';
        const values = ['John Doe', 30];

        connection.query(sql, values, (err, results) => {
            if (err) {
                console.error('Error inserting data:', err);
            } else {
                console.log('Inserted Row ID:', results.insertId);
                
                // Query to fetch data
                connection.query('SELECT * FROM users', (err, results) => {
                    if (err) {
                        console.error('Error fetching data:', err);
                    } else {
                        console.log('Users:', results);
                    }

                    // Close the connection
                    connection.end();
                });
            }
        });
    }
});

Step 4: Run the Application Node.js to MySQL

You can run your Node.js application by executing the following command in your terminal:

 node index.js

Explanation of the Code:

1. Import mysql2: We import the mysql2 package.
2. Create Connection: We establish a connection to the MySQL database by specifying the host, user, password, and database.
3. Connect: We connect to the database and handle any connection errors.
4. Query Execution: We execute an INSERT query to add new data and a SELECT query to retrieve data. The queries use placeholders (?) for safe parameter binding.
5. Close Connection: Finally, we close the connection to the database.

Additional Notes

• You can also use async/await with mysql2/promise for cleaner code when dealing with promises.
• Be sure to handle errors and close connections properly in real applications to avoid memory leaks and connection issues.
• There are also ORM libraries like Sequelize that you may want to consider for more complex applications, as they can simplify database interactions.

You can modify the configuration and queries according to your specific needs. This is just a foundational example to get you started with Node.js and MySQL.

Conclusion

Connecting Node.js to MySQL is straightforward thanks to the mysql package, which facilitates the development of data-driven applications. In this guide, we’ve covered the essential steps you need to follow to set up the connection and perform simple queries. As you delve deeper into Node.js and MySQL, you’ll uncover more advanced features like connection pooling, error handling, and asynchronous queries.

Feel free to experiment and build more complex applications as you grow your knowledge and skill set. Happy coding!