Add a Product (INSERT)

Your shop reads its products from shop.db. Now clients can add one: they send a POST to /products, the same path as the list, with the new product in the JSON body. app.use(express.json()), already in the file, puts that body in req.body, typed any. Your route saves it with an INSERT statement.

Here is an INSERT on another table, a list of newsletter subscribers:

const result = db.prepare("INSERT INTO subscribers (email) VALUES (?)").run("sam@example.com");
console.log(result.lastInsertRowid);   // the id the database chose for the new row

Three things matter. Each ? takes one value, in order, so whatever text the client sends stays a value and never becomes SQL. You leave the id out: the database picks the next free number, and result.lastInsertRowid tells you which. And there is no separate step to save: each statement is committed, which means saved for good, the moment .run finishes.

Starting from the shop's 8 products, your code must answer:

POST /products  {"name": "Vase", "price": 18, "category": "home"}  →  201  {"id": 9}
GET /products/9  →  200  {"id": 9, "name": "Vase", "price": 18, "category": "home", "stock": 0}
POST /products  {"name": "Candle", "price": 6}  →  201  {"id": 10}
GET /products?max_price=6  →  200  [{"id": 4, "name": "Pen", …}, {"id": 10, "name": "Candle", "price": 6, "category": null, "stock": 0}]

Your task: add the route POST /products. Read the body, insert the name, the price and the category (null if it is missing) with ? placeholders, and answer the new id with the status 201.

Assignment
Follow the Coding Tutorial to add the POST /products route, which saves a new product in the database.

Hint
The Candle has no category: data.category is undefined, and the database can't store that. Declare category with let and put null in its place: it is stored as NULL. Run the INSERT with .run, not .all: it gives back the object that has lastInsertRowid.