Prisma ORM setup in NextJS - Mini Project: Build & Apply

Prisma ORM setup

📖 Scenario: You are building a Next.js app that needs to store and retrieve user data from a database. To manage the database easily, you will set up Prisma ORM, which helps you work with databases using JavaScript code.

🎯 Goal: Set up Prisma ORM in a Next.js project by creating the Prisma schema, configuring the database connection, generating the Prisma client, and integrating it into the Next.js app.

📋 What You'll Learn

Create a Prisma schema file with a User model

Add a database connection URL variable

Generate the Prisma client

Create a Prisma client instance and export it for use in the app

💡 Why This Matters

🌍 Real World

Prisma ORM is widely used in web apps to simplify database access and management with type safety and easy queries.

💼 Career

Knowing how to set up and use Prisma ORM is valuable for full-stack developers working with Next.js and databases.

1

Create Prisma schema with User model

Create a file called schema.prisma inside the prisma folder. Inside it, write the datasource block with provider sqlite and url env("DATABASE_URL"). Then add a generator block for prisma-client-js. Finally, define a model User with fields: id Int @id @default(autoincrement()), email String @unique, and name String?.

NextJS

// Create prisma/schema.prisma file with datasource, generator, and User model
// Your code here

Hint

Remember to use env("DATABASE_URL") for the database URL and define the User model with the exact fields.

2

Add database connection URL in environment variables

In the root of your Next.js project, create a file called .env. Inside it, add the line DATABASE_URL="file:./dev.db" to set the SQLite database file path.

NextJS

datasource db {
  provider = "sqlite"
  url      = env("DATABASE_URL")
}

generator client {
  provider = "prisma-client-js"
}

model User {
  id    Int     @id @default(autoincrement())
  email String  @unique
  name  String?
}

# Add DATABASE_URL environment variable in .env file
# Your code here

Hint

Make sure the environment variable is named exactly DATABASE_URL and points to file:./dev.db.

3

Generate Prisma client

Run the command npx prisma generate in your terminal to generate the Prisma client based on your schema.

NextJS

datasource db {
  provider = "sqlite"
  url      = env("DATABASE_URL")
}

generator client {
  provider = "prisma-client-js"
}

model User {
  id    Int     @id @default(autoincrement())
  email String  @unique
  name  String?
}

# Run the command below in terminal
# Your code here

Hint

Use the exact command npx prisma generate to create the Prisma client.

4

Create and export Prisma client instance

In your Next.js project, create a file called lib/prisma.ts. Inside it, import PrismaClient from @prisma/client. Then create a constant called prisma as a new PrismaClient() instance. Finally, export prisma as the default export.

NextJS

// Create lib/prisma.ts file
// Your code here

Hint

Make sure to import PrismaClient, create an instance named prisma, and export it as default.

Practice

1. What is the primary purpose of the schema.prisma file in a Next.js project using Prisma ORM?

easy

A. To write API routes for Next.js

B. To define the database models and their relationships

C. To configure Next.js page routing

D. To style the application components

Solution

1. Step 1: Understand the role of schema.prisma

   This file is used to define the data models and how they relate to each other in the database.

2. Step 2: Differentiate from other files in Next.js

   API routes and page routing are handled by Next.js files, not schema.prisma. Styling is done with CSS or styling libraries.

3. Final Answer:

   To define the database models and their relationships -> Option B

4. Quick Check:

   schema.prisma = data models [OK]

Hint: Remember: schema.prisma defines your database structure [OK]

Common Mistakes:

• Confusing schema.prisma with API route files
• Thinking schema.prisma handles styling
• Assuming schema.prisma manages Next.js routing

2. Which of the following is the correct way to import and instantiate the Prisma Client in a Next.js API route?

easy

A. import { PrismaClient } from '@prisma/client'; const prisma = new PrismaClient();

B. const prisma = require('@prisma/client').PrismaClient();

C. import prisma from '@prisma/client'; const client = new prisma();

D. import Prisma from 'prisma'; const prisma = Prisma.Client();

Solution

1. Step 1: Check the correct import syntax for Prisma Client

   The official way is to import PrismaClient as a named import from '@prisma/client'.

2. Step 2: Instantiate PrismaClient correctly

   Use the new keyword to create an instance: new PrismaClient().

3. Final Answer:

   import { PrismaClient } from '@prisma/client'; const prisma = new PrismaClient(); -> Option A

4. Quick Check:

   Correct import and instantiation = import { PrismaClient } from '@prisma/client'; const prisma = new PrismaClient(); [OK]

Hint: Use named import and new keyword for PrismaClient [OK]

Common Mistakes:

• Using require() instead of import
• Calling PrismaClient as a function without new
• Incorrect import paths or default imports

3. Given the following Prisma model in schema.prisma:

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

What will be the result of this Prisma Client query?

const posts = await prisma.post.findMany({ where: { published: true } });
console.log(posts);

medium

A. A single post object with published true

B. An array of all posts regardless of published status

C. An error because 'published' is not a valid field

D. An array of posts where published is true

Solution

1. Step 1: Understand the Prisma model and query

   The model has a Boolean field published. The query filters posts where published is true.

2. Step 2: Analyze the query result

   findMany returns an array of all matching posts, so it returns all posts with published: true.

3. Final Answer:

   An array of posts where published is true -> Option D

4. Quick Check:

   findMany with where filter = array filtered by condition [OK]

Hint: findMany returns arrays filtered by where conditions [OK]

Common Mistakes:

• Expecting a single object instead of an array
• Ignoring the where filter and expecting all posts
• Thinking 'published' field does not exist

4. You wrote this code in a Next.js API route:

import { PrismaClient } from '@prisma/client';
const prisma = new PrismaClient();

export default async function handler(req, res) {
  const user = await prisma.user.findUnique({ where: { id: req.query.id } });
  res.json(user);
}

But you get an error: TypeError: Cannot read property 'id' of undefined. What is the likely cause?

medium

A. PrismaClient is not instantiated correctly

B. The findUnique method does not exist

C. The req.query object is undefined or missing id

D. You forgot to import res from Next.js

Solution

1. Step 1: Identify the error cause

   The error says Cannot read property 'id' of undefined, meaning req.query is undefined or id is missing.

2. Step 2: Check the API route usage

   Ensure the request URL includes a query parameter ?id=someValue so req.query.id exists.

3. Final Answer:

   The req.query object is undefined or missing id -> Option C

4. Quick Check:

   Missing query param causes undefined error [OK]

Hint: Check if query parameters exist before accessing them [OK]

Common Mistakes:

• Assuming PrismaClient instantiation causes this error
• Thinking findUnique method is invalid
• Trying to import res object explicitly

5. You want to add a new model Comment related to Post in your Prisma schema, where each comment belongs to one post. Which of the following schema additions correctly sets up this relationship?

hard

A. model Comment {
id Int @id @default(autoincrement())
content String
postId Int
post Post @relation(fields: [postId], references: [id])
}

model Post {
id Int @id @default(autoincrement())
title String
comments Comment[]
}

B. model Comment {
id Int @id @default(autoincrement())
content String
post Post
}

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

C. model Comment {
id Int @id @default(autoincrement())
content String
postId Int
}

model Post {
id Int @id @default(autoincrement())
title String
comments Comment[]
}

D. model Comment {
id Int @id @default(autoincrement())
content String
postId Int
post Post
}

model Post {
id Int @id @default(autoincrement())
title String
comments Comment[]
}

Solution

1. Step 1: Understand Prisma relations syntax

   To relate Comment to Post, Comment needs a foreign key postId and a relation field post with @relation specifying fields and references.

2. Step 2: Check the Post model for back relation

   Post should have a comments field as an array of Comment to represent one-to-many relation.

3. Final Answer:

   Option A correctly defines the foreign key, relation, and back relation -> Option A

4. Quick Check:

   Relation fields with @relation and back array = model Comment { id Int @id @default(autoincrement()) content String postId Int post Post @relation(fields: [postId], references: [id]) } model Post { id Int @id @default(autoincrement()) title String comments Comment[] } [OK]

Hint: Use @relation with fields and references for foreign keys [OK]

Common Mistakes:

• Omitting @relation attribute causing errors
• Not defining back relation array in Post
• Missing foreign key field postId in Comment