ORM concept (Sequelize, Prisma overview) in Node.js - Mini Project: Build & Apply

Basic ORM Concept with Sequelize in Node.js

📖 Scenario: You are building a simple Node.js app to manage a list of books in a library. Instead of writing raw database queries, you will use an ORM (Object-Relational Mapping) tool called Sequelize to interact with the database easily.This project will help you understand how to set up data models and perform basic operations using Sequelize, a popular ORM for Node.js.

🎯 Goal: Create a Sequelize model for books, configure a connection, and write code to add and list books using ORM methods.

📋 What You'll Learn

Create a Sequelize model called Book with fields title (string) and author (string).

Set up a Sequelize connection to an SQLite database.

Write code to add a new book record using the Book.create() method.

Write code to retrieve all books using the Book.findAll() method.

💡 Why This Matters

🌍 Real World

ORMs like Sequelize are used in many Node.js applications to simplify database interactions by mapping database tables to JavaScript objects.

💼 Career

Understanding ORM concepts is essential for backend developers working with databases, improving productivity and code maintainability.

1

DATA SETUP: Import Sequelize and create a Sequelize instance

Write code to import Sequelize from the sequelize package and create a new Sequelize instance called sequelize that connects to an SQLite database named library.db.

Node.js

const { Sequelize } = require('sequelize');

// Your code here

Hint

Use new Sequelize({ dialect: 'sqlite', storage: 'library.db' }) to create the connection.

2

CONFIGURATION: Define the Book model with title and author fields

Using the sequelize instance, define a model called Book with two string fields: title and author. Assign this model to a constant named Book.

Node.js

const { Sequelize } = require('sequelize');

const sequelize = new Sequelize({
  dialect: 'sqlite',
  storage: 'library.db'
});

// Define the Book model below
// Your code here

Hint

Use sequelize.define('Book', { title: { type: Sequelize.STRING }, author: { type: Sequelize.STRING } }).

3

CORE LOGIC: Add a new book record using Book.create()

Write code to add a new book with title set to 'The Great Gatsby' and author set to 'F. Scott Fitzgerald' using the Book.create() method. Assign the result to a constant named newBook.

Node.js

const { Sequelize } = require('sequelize');

const sequelize = new Sequelize({
  dialect: 'sqlite',
  storage: 'library.db'
});

const Book = sequelize.define('Book', {
  title: {
    type: Sequelize.STRING
  },
  author: {
    type: Sequelize.STRING
  }
});

// Add a new book record below
// Your code here

Hint

Use Book.create({ title: 'The Great Gatsby', author: 'F. Scott Fitzgerald' }) and assign it to newBook.

4

COMPLETION: Retrieve all books using Book.findAll()

Write code to retrieve all book records using Book.findAll() and assign the result to a constant named allBooks.

Node.js

const { Sequelize } = require('sequelize');

const sequelize = new Sequelize({
  dialect: 'sqlite',
  storage: 'library.db'
});

const Book = sequelize.define('Book', {
  title: {
    type: Sequelize.STRING
  },
  author: {
    type: Sequelize.STRING
  }
});

const newBook = Book.create({
  title: 'The Great Gatsby',
  author: 'F. Scott Fitzgerald'
});

// Retrieve all books below
// Your code here

Hint

Use Book.findAll() and assign it to allBooks.

Practice

1. What is the main purpose of an ORM like Sequelize or Prisma in Node.js?

easy

A. To simplify database operations by using JavaScript code instead of raw SQL

B. To replace Node.js as a runtime environment

C. To create user interfaces for web applications

D. To manage server hardware resources

Solution

1. Step 1: Understand what ORM stands for

   ORM means Object-Relational Mapping, which helps translate code into database queries.

2. Step 2: Identify ORM's role in Node.js

   Sequelize and Prisma let developers write JavaScript code to interact with databases instead of writing SQL directly.

3. Final Answer:

   To simplify database operations by using JavaScript code instead of raw SQL -> Option A

4. Quick Check:

   ORM = Simplify database code [OK]

Hint: ORM means code replaces SQL for easier database work [OK]

Common Mistakes:

• Thinking ORM replaces Node.js runtime
• Confusing ORM with UI tools
• Assuming ORM manages hardware

2. Which of the following is the correct way to define a model in Sequelize?

easy

A. createModel('User', { name: 'string' })

B. sequelize.define('User', { name: DataTypes.STRING })

C. new Model('User', { name: String })

D. Model.defineUser({ name: DataType.String })

Solution

1. Step 1: Recall Sequelize model definition syntax

   Sequelize uses sequelize.define(modelName, attributes) to create models.

2. Step 2: Match options with correct syntax

   sequelize.define('User', { name: DataTypes.STRING }) matches the correct method and uses DataTypes.STRING properly.

3. Final Answer:

   sequelize.define('User', { name: DataTypes.STRING }) -> Option B

4. Quick Check:

   Sequelize model = sequelize.define() [OK]

Hint: Sequelize models use sequelize.define() with DataTypes [OK]

Common Mistakes:

• Using 'new Model' instead of sequelize.define
• Incorrect DataTypes usage
• Wrong method names like createModel

3. Given this Prisma schema snippet:

model Post {
  id    Int     @id @default(autoincrement())
  title String
  published Boolean @default(false)
}

What will be the default value of published when a new Post is created without specifying it?

medium

A. false

B. true

C. null

D. undefined

Solution

1. Step 1: Read the Prisma model definition

   The field published is Boolean with @default(false), meaning it defaults to false.

2. Step 2: Understand default behavior on creation

   If no value is given for published, Prisma sets it to the default, which is false.

3. Final Answer:

   false -> Option A

4. Quick Check:

   Prisma default Boolean = false [OK]

Hint: Look for @default() in Prisma schema for default values [OK]

Common Mistakes:

• Assuming default is true without checking
• Thinking default is null or undefined
• Ignoring @default directive

4. You wrote this Sequelize code:

const User = sequelize.define('User', {
  username: Sequelize.STRING,
  age: Sequelize.INTEGER
});

But you get an error: Sequelize.STRING is not a constructor. What is the likely fix?

medium

A. Change Sequelize.STRING to 'string' (a string literal)

B. Remove the model definition and use raw SQL instead

C. Import DataTypes from Sequelize and use DataTypes.STRING instead

D. Rename 'User' to 'Users' in define method

Solution

1. Step 1: Identify the cause of the error

   Sequelize.STRING is not a constructor because Sequelize exports DataTypes separately.

2. Step 2: Correct usage of DataTypes

   You should import DataTypes from Sequelize and use DataTypes.STRING and DataTypes.INTEGER in model definitions.

3. Final Answer:

   Import DataTypes from Sequelize and use DataTypes.STRING instead -> Option C

4. Quick Check:

   Use DataTypes.STRING, not Sequelize.STRING [OK]

Hint: Use DataTypes from Sequelize for types, not Sequelize directly [OK]

Common Mistakes:

• Using Sequelize.STRING instead of DataTypes.STRING
• Trying to fix by renaming model
• Switching to raw SQL unnecessarily

5. You want to fetch all users with their posts using Prisma. Which code snippet correctly fetches users including their posts?

hard

A. const users = await prisma.user.findAll({ include: ['posts'] });

B. const users = await prisma.user.findMany({ select: { posts: false } });

C. const users = await prisma.user.findMany({ where: { posts: null } });

D. const users = await prisma.user.findMany({ include: { posts: true } });

Solution

1. Step 1: Recall Prisma syntax for including related models

   Prisma uses include: { relatedModel: true } to fetch related data.

2. Step 2: Check each option for correct syntax

   const users = await prisma.user.findMany({ include: { posts: true } }); uses include: { posts: true } which is correct. const users = await prisma.user.findMany({ select: { posts: false } }); excludes posts, C filters by posts null, D uses wrong method name.

3. Final Answer:

   const users = await prisma.user.findMany({ include: { posts: true } }); -> Option D

4. Quick Check:

   Prisma include related = include: { posts: true } [OK]

Hint: Use include: { relatedModel: true } to fetch relations in Prisma [OK]

Common Mistakes:

• Using findAll instead of findMany in Prisma
• Using select to exclude instead of include to fetch
• Wrong syntax for including relations