Integrating NestJS with Sequelize ORM and PostgreSQL

“Learn how to integrate NestJS with Sequelize ORM and PostgreSQL step-by-step. Simplify database operations, create models, and build robust APIs with this beginner-friendly guide. Perfect for developers working with TypeScript and backend frameworks.”

Introduction: Making Apps Talk to Databases

Imagine you have a big toy box (your database), and you need a friendly robot (NestJS) to help you find and organize your toys quickly. To make this robot even smarter, you give it a cool translator tool called Sequelize ORM. It helps the robot understand the language of your toy box, PostgreSQL.

In this blog, we’ll learn how to set up a NestJS app with Sequelize ORM to work with PostgreSQL. Don’t worry; I’ll explain it like a fun story!

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1. Why NestJS + Sequelize + PostgreSQL?

• NestJS: The clever robot that organizes your app. It’s great at handling tasks.
• Sequelize ORM: The translator that helps NestJS talk to the database in simple sentences.
• PostgreSQL: The toy box where all your toys (data) live.

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2. Setting It All Up: Step-by-Step

Step 1: Start a New NestJS Project

First, create a new NestJS project by running:

npx @nestjs/cli new my-app
cd my-app

This creates your robot (NestJS) with a basic setup.

Step 2: Install Necessary Packages

We need to install Sequelize and PostgreSQL packages:

npm install @nestjs/sequelize sequelize sequelize-typescript pg pg-hstore

Here’s what they do:

• @nestjs/sequelize: Makes Sequelize work with NestJS.
• sequelize: The ORM itself.
• sequelize-typescript: Adds TypeScript support for Sequelize.
• pg and pg-hstore: Help Sequelize connect to PostgreSQL.

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Step 3: Set Up the Database

Make sure PostgreSQL is installed on your computer. Create a database:

CREATE DATABASE my_app_db;

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Step 4: Configure Sequelize in NestJS

In src/app.module.ts, configure Sequelize:

import { Module } from '@nestjs/common';
import { SequelizeModule } from '@nestjs/sequelize';

@Module({
  imports: [
    SequelizeModule.forRoot({
      dialect: 'postgres',
      host: 'localhost',
      port: 5432,
      username: 'your_username',
      password: 'your_password',
      database: 'my_app_db',
      autoLoadModels: true,
      synchronize: true,
    }),
  ],
})
export class AppModule {}

• autoLoadModels: true: Automatically loads all models.
• synchronize: true: Syncs models with the database (great for development).

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Step 5: Create a Toy (Model)

Let’s create a model to represent toys in our database:

nest g module toys
nest g service toys
nest g controller toys

Then create a toy.model.ts in the toys folder:

import { Table, Column, Model } from 'sequelize-typescript';

@Table
export class Toy extends Model {
  @Column
  name: string;

  @Column
  color: string;

  @Column
  price: number;
}

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Step 6: Connect Model to the App

In toys.module.ts, add the model:

import { Module } from '@nestjs/common';
import { SequelizeModule } from '@nestjs/sequelize';
import { ToysService } from './toys.service';
import { ToysController } from './toys.controller';
import { Toy } from './toy.model';

@Module({
  imports: [SequelizeModule.forFeature([Toy])],
  providers: [ToysService],
  controllers: [ToysController],
})
export class ToysModule {}

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Step 7: Build API Endpoints

In toys.controller.ts, add basic CRUD endpoints:

import { Controller, Get, Post, Body } from '@nestjs/common';
import { ToysService } from './toys.service';
import { Toy } from './toy.model';

@Controller('toys')
export class ToysController {
  constructor(private readonly toysService: ToysService) {}

  @Post()
  create(@Body() toy: Toy) {
    return this.toysService.createToy(toy);
  }

  @Get()
  findAll() {
    return this.toysService.getAllToys();
  }
}

In toys.service.ts, write methods:

import { Injectable } from '@nestjs/common';
import { InjectModel } from '@nestjs/sequelize';
import { Toy } from './toy.model';

@Injectable()
export class ToysService {
  constructor(@InjectModel(Toy) private toyModel: typeof Toy) {}

  createToy(toy: Toy) {
    return this.toyModel.create(toy);
  }

  getAllToys() {
    return this.toyModel.findAll();
  }
}

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Step 8: Test Your API

Run the app:

npm run start

Test with tools like Postman or Thunder Client. You can create toys and view them!

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3. Interview Questions and Answers

Q1: What is Sequelize ORM, and why is it used?

• A: Sequelize ORM is a library that helps manage database operations using JavaScript/TypeScript instead of SQL queries. It simplifies CRUD operations and supports multiple databases like PostgreSQL.

Q2: How do you connect Sequelize with PostgreSQL in NestJS?

• A: Install required packages (@nestjs/sequelize, sequelize, pg), then configure SequelizeModule in app.module.ts with database credentials.

Q3: What does autoLoadModels do in SequelizeModule configuration?

• A: It automatically loads all models into Sequelize, so you don’t need to manually register each one.

Q4: What is the purpose of sequelize-typescript?

• A: It adds TypeScript support to Sequelize, allowing you to define models as TypeScript classes.

Q5: How do you sync models with the database in NestJS?

• A: Use synchronize: true in the SequelizeModule configuration. It ensures models match the database schema (only recommended for development).

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4. Companies Asking About NestJS + Sequelize + PostgreSQL

1. Globant
2. TCS (Tata Consultancy Services)
3. Infosys
4. Wipro
5. Cognizant

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5. Conclusion

Integrating NestJS with Sequelize and PostgreSQL is like setting up a robot to help organize your toy box. By following these steps, you’ll have a powerful system that’s ready to handle data with ease. Good luck, and happy coding! 🚀

Interested in learning more about Microservices and NestJS? Check out our latest blogs for more in-depth guides, tutorials, and best practices on building scalable applications with NestJS and microservices.