How to connect MySQL in your backend project (NestJS + Prisma)

[WILD]

Hi! While working on a backend project, I ran into a simple but annoying problem — I couldn’t find a clear and complete guide on connecting MySQL to a basic backend project.

Most tutorials either:

• skip important steps
• assume too much prior knowledge
• or don’t explain why things work the way they do

So in this guide, I’ll show you:

• how to connect MySQL using NestJS + Prisma
• how it works under the hood
• and how to use it in a monorepo setup

---

Why Prisma?​

Before we start — a quick note.

Prisma is not just another ORM. It provides:

• type-safe database queries
• auto-generated client based on schema
• better developer experience than classic ORMs like TypeORM

In simple terms: less SQL, fewer runtime errors, more productivity.

Create a NestJS project​

npm i -g @nestjs/clinest new my-backend-projectcd my-backend-projectnpm install


Run it:

npm run start

Install Prisma​

npm install prisma --save-devnpm install @prisma/client


Initialize Prisma:

npx prisma init


Best practice: always use npx prisma instead of global CLI

---

After initialization, you’ll get:​

• schema.prisma — database schema & connection
• .env — environment variables
• prisma.config.ts — project config

---

Configure MySQL​

By default Prisma uses PostgreSQL or SQLite. We switch to MySQL. Now open .env:

DATABASE_URL="mysql://rootassword@localhost:3306/my_db"
DATABASE_USER="root"
DATABASE_PASSWORD="password"
DATABASE_NAME="my_db"
DATABASE_HOST="localhost"
DATABASE_PORT=3306


And now open schema.prisma:

generator client {
provider = "prisma-client"
output = "../generated/prisma"
moduleFormat = "cjs"
}

datasource db {
provider = "mysql"
}


This is the standard connection format for MySQL in Prisma

---

Generate Prisma Client​

npx prisma generate


Prisma generates a type-safe client based on your schema.
This means your queries are validated at compile time.

---

Create PrismaService​

import "dotenv/config";
import { PrismaMariaDb } from "@prisma/adapter-mariadb";
import { PrismaClient } from "../generated/prisma/client";
import { Injectable } from "@nestjs/common";

@Injectable()
export class PrismaService extends PrismaClient{
constructor(){
const adapter = new PrismaMariaDb({
host: process.env.DATABASE_HOST,
user: process.env.DATABASE_USER,
password: process.env.DATABASE_PASSWORD,
database: process.env.DATABASE_NAME,
connectionLimit: 5,
});
super({adapter})
}
}


Why this is needed:

• integrates Prisma into Nest lifecycle
• ensures proper connection handling
• avoids memory leaks in production

---

Create PrismaModule​

import { Module } from '@nestjs/common';
import { PrismaService } from './prisma.service';

@Module({
providers: [PrismaService],
exports: [PrismaService],
})
export class PrismaModule {}

---

Use Prisma in your service​

We’ll write our service in the constructor. I’ll show you how to use it with an example:

import { Injectable } from '@nestjs/common';
import { PrismaService } from 'prisma/prisma.service';
import { TodoDTO } from './dto/todo.dto';

@Injectable()
export class TodoService {
constructor(private readonly todoService: PrismaService){} //this is mandatory

public getOne(id:number){
return this.todoService.todo.findFirst(
{
where: {id}
}
)
}

public getAll(){
return this.todoService.todo.findMany()
}

public create(data: TodoDTO){
return this.todoService.todo.create({data: data})
}

public upgrade(id: number, data: TodoDTO){
return this.todoService.todo.update({
where: {id},
data: data
})
}

public delete(id:number){
return this.todoService.todo.delete(
{
where: {id}
}
)
}

}


This is how Prisma is typically used in NestJS services

---

Run migrations​

npx prisma migrate dev --name initnpx prisma generate

Monorepo setup (short explanation)​

In a monorepo:

• keep Prisma in a separate package/lib
• export only services (not raw client)
• reuse across apps

This helps:

• isolate DB logic
• simplify scaling
• switch databases easier

Bonus — Official docs​

• NestJS
• Prisma

Also, especially for you, I’ve included a reference card so you can remember and save it for future use. In this card, I’ve gathered all the material to make things easier for you.

If this guide helped you — feel free to support the post.
Thanks for your attention!