To use MySQL in an Express app, set up a connection, run queries securely, and handle errors properly. First, install MySQL and create a database. Next, install the mysql package and configure the connection using a db.js file. Then, use parameterized queries in routes to prevent SQL injection. Additionally, handle errors explicitly in callbacks or with try-catch blocks. Optionally, wrap queries in promises for cleaner async/await code. Finally, always test edge cases and log errors for debugging.
If you're building a Node.js app with Express and want to use MySQL as your database, the setup is straightforward once you know the flow. The main pieces involve connecting your Express app to the MySQL server, running queries, and handling them properly—especially avoiding SQL injection.
Setting Up MySQL in Your Express App
First, make sure you have a MySQL server running locally or remotely. You can install MySQL via tools like XAMPP or directly from the MySQL website. Once it's up, create a new database and table that your Express app will interact with.
In your Node.js project, install the MySQL package:
npm install mysql
Then, set up a connection object in your app (usually in a db.js or similar config file):
const mysql = require('mysql');
const connection = mysql.createConnection({
host: 'localhost',
user: 'root',
password: '',
database: 'myapp_db'
});
connection.connect((err) => {
if (err) throw err;
console.log('MySQL connected...');
});
module.exports = connection;This sets up a basic connection. Some people prefer using connection pools for better performance, especially under heavy load. That’s something you might want to explore later.
Querying the Database from Express Routes
Once connected, you’ll want to run SELECT, INSERT, UPDATE, DELETE statements from your routes.
Let’s say you have a /users route that fetches all users:
const express = require('express');
const router = express.Router();
const db = require('./db');
router.get('/users', (req, res) => {
let sql = 'SELECT * FROM users';
db.query(sql, (err, results) => {
if (err) throw err;
res.json(results);
});
});You can also pass values dynamically, like inserting a new user:
router.post('/users', (req, res) => {
let newUser = { name: 'John Doe', email: 'john@example.com' };
let sql = 'INSERT INTO users SET ?';
db.query(sql, newUser, (err, result) => {
if (err) throw err;
res.send('User added...');
});
});- Always use parameterized queries (
?) when passing dynamic data. - Avoid concatenating values into SQL strings to prevent SQL injection.
- Use
.query()method with proper placeholders.
This way, your code stays safe and readable.
Handling Errors and Edge Cases
Working with databases means things can go wrong—connection issues, query errors, missing rows, etc.
Some common issues include:
- Forgetting to escape input values
- Typos in column or table names
- Not closing connections (if using single connection)
- Trying to access rows that don’t exist
A good practice is to wrap your queries in try-catch blocks (especially when using async/await), or at least handle errors explicitly in callbacks.
For example:
db.query('SELECT * FROM users WHERE id = ?', [req.params.id], (err, results) => {
if (err) {
console.error(err);
return res.status(500).send('Database error');
}
if (results.length === 0) {
return res.status(404).send('User not found');
}
res.json(results[0]);
});Also, logging errors helps debug faster. Don’t just throw or ignore them unless you’re sure.
Using Promises or Async/Await (Optional but Cleaner)
If you're using a newer version of Node.js, consider wrapping your queries in promises or using async/await syntax for cleaner code.
Here’s how you can do it:
const util = require('util');
db.query = util.promisify(db.query).bind(db);
// Then inside an async function
try {
const results = await db.query('SELECT * FROM users');
res.json(results);
} catch (err) {
res.status(500).send(err);
}It makes your code easier to read and maintain, especially when dealing with multiple queries in sequence.
That’s basically it. It’s not complicated once you get the basics down—connect, query, handle errors, and optionally clean up with async patterns. Just remember to keep your queries secure and always test edge cases.
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