Mohit Decodes

*🗄️ Database Integration — MongoDB with Node.js*

Now you move from temporary data (arrays) → real database storage.

Backend apps must store data permanently.

That's where databases come in.

*🧠 What is a Database*

A database stores data persistently.

*Examples:*
- E-commerce: Products, orders
- Social media: Users, posts
- Banking app: Transactions

*Without database → data disappears when server restarts.*

*🍃 What is MongoDB*

MongoDB is a NoSQL database.

*Instead of tables → it stores documents (JSON-like data).*

*Example document:*

{
  "name": "Deepak",
  "role": "Developer",
  "age": 25
}

*Collection = group of documents*
*Database = group of collections*

*📦 Why MongoDB is Popular*

✅ *JSON-like data*
✅ *Flexible schema*
✅ *Works perfectly with JavaScript*
✅ *Scales easily*

*Common in MERN stack.*

*MERN = MongoDB + Express + React + Node*

*🔗 Connecting MongoDB with Node.js*

We use a library called Mongoose.

*Install:*

npm install mongoose

*⚡ Step 1 — Connect Database*

*Example:*

const mongoose = require("mongoose");

mongoose.connect("mongodb://127.0.0.1:27017/myapp")
.then(() => console.log("MongoDB Connected"))
.catch(err => console.log(err));

*Now Node server is connected to MongoDB.*

*🧩 Step 2 — Create Schema*

*Schema defines data structure.*

*Example:*

const userSchema = new mongoose.Schema({
  name: String,
  age: Number
});

*📄 Step 3 — Create Model*

*Model allows database operations.*

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

*➕ Step 4 — Create Data*

app.post("/users", async (req, res) => {
  const user = new User({
    name: req.body.name,
    age: req.body.age
  });

  await user.save();
  res.json(user);
});

*🔍 Step 5 — Fetch Data*

app.get("/users", async (req, res) => {
  const users = await User.find();
  res.json(users);
});

*❌ Step 6 — Delete Data*

app.delete("/users/:id", async (req, res) => {
  await User.findByIdAndDelete(req.params.id);
  res.json({ message: "User deleted" });
});

*✏️ Step 7 — Update Data*

app.put("/users/:id", async (req, res) => {
  const user = await User.findByIdAndUpdate(
    req.params.id,
    req.body,
    { new: true }
  );
  res.json(user);
});

*🔄 Full Backend Flow Now*

*React → API request*
*Express → Handles route*
*Mongoose → Talks to MongoDB*
*MongoDB → Stores data*

*⚠️ Common Beginner Mistakes*

- *Forgetting to install mongoose*
- *Not using async/await*
- *Wrong MongoDB URL*
- *Not validating schema*

*🧪 Mini Practice Task*

*Build Product API with MongoDB*

*Routes:*
- POST /products
- GET /products
- PUT /products/:id
- DELETE /products/:id

*Fields:*
name
price
category

✅ *Mini Practice Task – Solution*

This solution implements:

✔ POST /products → Add product
✔ GET /products → Fetch products
✔ PUT /products/:id → Update product
✔ DELETE /products/:id → Delete product

🟢 *Step 1 — Install Required Packages*

npm init -y
npm install express mongoose cors

📄 *Step 2 — Create server.js*

const express = require("express");
const mongoose = require("mongoose");
const cors = require("cors");

const app = express();

app.use(cors());
app.use(express.json());

/* ---------------- DATABASE CONNECTION ---------------- */

mongoose.connect("mongodb://127.0.0.1:27017/productdb")
.then(() => console.log("MongoDB connected"))
.catch(err => console.log(err));

/* ---------------- PRODUCT SCHEMA ---------------- */

const productSchema = new mongoose.Schema({
name: String,
price: Number,
category: String
});

const Product = mongoose.model("Product", productSchema);

/* ---------------- ROUTES ---------------- */

/* CREATE PRODUCT */
app.post("/products", async (req, res) => {

const product = new Product({
name: req.body.name,
price: req.body.price,
category: req.body.category
});

await product.save();

res.json(product);
});

/* GET PRODUCTS */
app.get("/products", async (req, res) => {

const products = await Product.find();

res.json(products);
});

/* UPDATE PRODUCT */
app.put("/products/:id", async (req, res) => {

const product = await Product.

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