Inserting into mysql using express and nodejs

// file: server.js
const express = require('express');
const db = require('./db');
const app = express();

// you may wish to reconsider the use of .get at some stage
// what happens when you want to retrieve an item?
app.get('/models', (req, res) => {
  // learn about validation when you're comfortable with basics
  // this is especially important for public facing apps
  if (!req.query.manufacturer || !req.query.type || !req.query.cost) {
    return res.status(400).send('wrong input!'); // super helpful error messages
  }

  const public = req.query.public || true; // set defaults
  const { manufacturer, type, cost } = req.query;

  // when you're more comfortable, learn about abstractions + Service pattern
  // removing DB queries from route handlers, pushing the responsibility to a Service.
  db.query(
    'INSERT INTO car_models(manufacturer,type,cost,public) VALUES (?,?,?,?)',
    // learn about SQL injection, I **hope** the mysql package author considered it.
    [manufacturer, type, cost, public],
    (err, results) => {
      if (err) {
        console.error(err);
        return res.status(500).send('oh no');
      }

      return res.status(201).send(`Created ID: ${results.insertId}`);
    }
  );
});

app.listen(3000, () =>
  console.log('service started... accepting requests on http://localhost:3000')
);

/**
 *  File: db.js
 *  Responsibility: connect to MySQL
 *  Note: you could use an ORM here (**could** not always **should**)
 */
const mysql = require('mysql');
const connection = mysql.createConnection({
  host: 'localhost',
  user: 'develop',
  password: 'development',
  database: 'cars',
  port: 3306,
});

connection.connect((err) => {
  if (err) {
    console.error(`MySQL: Failed to connect to MySQL: ${err.message}`, err);
    return;
  }

  console.log('MySQL: Successfully connected to MySQL');

  connection.query(`CREATE TABLE IF NOT EXISTS car_models (
    id INT PRIMARY KEY AUTO_INCREMENT,
    manufacturer VARCHAR(30),
    type VARCHAR(10),
    cost BIGINT,
    public BOOLEAN
  );`);
});

module.exports = connection;

I had another example in mind, for the simplicity I've kept a style similar to yours, I hope this helps your understanding of it.

If there's anything you're unsure about, I recommend researching it. I don't recommend researching everything upfront. I tend to research things as/when I need them, or whenever I get the chance. (commuting for example)

You'll learn more through practice than researching, although it's important to find some form of balance. If not, you'll end up learning how to do something in a language and be restricted to only that language and only a small subset of the languages capabilities. (maybe, maybe not).

Adding a new car model is as simple as: curl http://localhost:3000/models?manufacturer=bmw&type=m3&cost=10000

Or, try opening http://localhost:3000/models?manufacturer=bmw&type=m3&cost=10000 in whatever browser you use (when it's running), and see what happens. You may find the browser (or Postman), will be easier to work with. Or you may not.

There's one very important part: no sessions, no cookies, no knowledge of the last request, nothing. This is stateless. For simple operations, there's no need to introduce such mechanisms as it's simply not required.

I'd suggest learning how Express.js can be structured (it's very flexible), there's patterns and best practices that you can follow, but maybe wait until you're comfortable with the language first, otherwise it can be a rabbit hole.

My final point, learn about the differences in stateless and stateful systems. Don't spend hours, take maybe 5 minutes so you understand the key concepts behind each. You can then use that knowledge to make your own decision about stateless vs stateful.

Something I wished I learned sooner: to solve a problem, you need to understand the problem you're trying to solve. Sounds basic, but I still get this wrong occasionally.

Good luck and all the best!