CRUD Operations with Database

Now that you know how to connect to databases, it's time to build a complete **CRUD** application. CRUD stands for Create, Read, Update, Delete – the four basic operations for persistent storage. In this chapter, we'll build a complete REST API for a simple resource (like products or posts) using Express and a database.

What is CRUD?

Operation	HTTP Method	Description
Create	POST	Add a new resource
Read	GET	Retrieve resources (single or list)
Update	PUT / PATCH	Modify an existing resource
Delete	DELETE	Remove a resource

Think of CRUD as the foundation of any data-driven application. Almost everything you build will involve these four operations.

Project Setup

mkdir crud-api
cd crud-api
npm init -y
npm install express mongoose dotenv
npm install --save-dev nodemon

Complete CRUD Example with MongoDB/Mongoose

1. Model (models/Product.js)

const mongoose = require('mongoose');

const productSchema = new mongoose.Schema({
  name: { type: String, required: true, trim: true },
  price: { type: Number, required: true, min: 0 },
  description: { type: String, maxlength: 500 },
  category: { type: String, required: true },
  inStock: { type: Boolean, default: true },
  createdAt: { type: Date, default: Date.now }
});

module.exports = mongoose.model('Product', productSchema);

2. Database Connection (config/db.js)

const mongoose = require('mongoose');

const connectDB = async () => {
  try {
    await mongoose.connect(process.env.MONGODB_URI);
    console.log('MongoDB connected');
  } catch (err) {
    console.error(err);
    process.exit(1);
  }
};

module.exports = connectDB;

3. Complete CRUD Routes (routes/products.js)

const express = require('express');
const Product = require('../models/Product');
const router = express.Router();

<!-- CREATE: POST /products -->
router.post('/', async (req, res) => {
  try {
    const product = new Product(req.body);
    const savedProduct = await product.save();
    res.status(201).json(savedProduct);
  } catch (err) {
    res.status(400).json({ error: err.message });
  }
});

<!-- READ ALL: GET /products -->
router.get('/', async (req, res) => {
  try {
    const products = await Product.find().sort({ createdAt: -1 });
    res.json(products);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

<!-- READ SINGLE: GET /products/:id -->
router.get('/:id', async (req, res) => {
  try {
    const product = await Product.findById(req.params.id);
    if (!product) {
      return res.status(404).json({ error: 'Product not found' });
    }
    res.json(product);
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

<!-- UPDATE: PUT /products/:id -->
router.put('/:id', async (req, res) => {
  try {
    const product = await Product.findByIdAndUpdate(
      req.params.id,
      req.body,
      { new: true, runValidators: true }
    );
    if (!product) {
      return res.status(404).json({ error: 'Product not found' });
    }
    res.json(product);
  } catch (err) {
    res.status(400).json({ error: err.message });
  }
});

<!-- DELETE: DELETE /products/:id -->
router.delete('/:id', async (req, res) => {
  try {
    const product = await Product.findByIdAndDelete(req.params.id);
    if (!product) {
      return res.status(404).json({ error: 'Product not found' });
    }
    res.status(204).send();
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

module.exports = router;

4. Main App File (app.js)

require('dotenv').config();
const express = require('express');
const connectDB = require('./config/db');
const productRoutes = require('./routes/products');

<!-- Connect to database -->
connectDB();

const app = express();
app.use(express.json());

<!-- Routes -->
app.use('/api/products', productRoutes);

<!-- 404 handler -->
app.use((req, res) => {
  res.status(404).json({ error: 'Route not found' });
});

<!-- Error handler -->
app.use((err, req, res, next) => {
  console.error(err);
  res.status(500).json({ error: 'Internal server error' });
});

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});

Two Minute Drill

CRUD = Create (POST), Read (GET), Update (PUT), Delete (DELETE).

Always validate input and handle errors gracefully.

Use appropriate HTTP status codes (201 for created, 404 for not found, etc.).

Organize routes using Express Router for clean code.

Test your API with tools like Postman or Insomnia.

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