CRUD with Prisma in NestJS - Mini Project: Build & Apply

CRUD with Prisma in NestJS

📖 Scenario: You are building a simple backend API for managing books in a library. Each book has a title and an author. You will use NestJS with Prisma to create, read, update, and delete books in the database.

🎯 Goal: Build a NestJS service that uses Prisma to perform CRUD operations on a Book model with title and author fields.

📋 What You'll Learn

Create a Prisma schema with a Book model having id, title, and author fields

Set up Prisma Client in NestJS

Implement CRUD methods in a NestJS service using Prisma Client

Use proper TypeScript types and async/await syntax

💡 Why This Matters

🌍 Real World

Backend developers often use Prisma with NestJS to build APIs that interact with databases easily and safely.

💼 Career

Knowing how to perform CRUD operations with Prisma in NestJS is a common requirement for backend developer roles.

1

Define the Prisma Book model

Create a Prisma schema file schema.prisma with a Book model that has an id field as an auto-incrementing integer primary key, a title field of type String, and an author field of type String.

NestJS

// Define the Book model in schema.prisma

// Your code here

Hint

Use model Book { ... } syntax. The id should be Int with @id and @default(autoincrement()).

2

Set up Prisma Client in NestJS service

In your NestJS service file books.service.ts, import PrismaClient from @prisma/client and create a private readonly property called prisma initialized with new PrismaClient().

NestJS

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

// Import PrismaClient and create prisma property
// Your code here

Hint

Use import { PrismaClient } from '@prisma/client' and create private readonly prisma = new PrismaClient(); inside the service class.

3

Implement the createBook method

Add an async method called createBook in BooksService that takes a parameter data with title and author strings, and uses this.prisma.book.create to create and return a new book record.

NestJS

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

import { Injectable } from '@nestjs/common';
import { PrismaClient } from '@prisma/client';

@Injectable()
export class BooksService {
  private readonly prisma = new PrismaClient();

  // Add async createBook method here
  // Your code here
}

Hint

Use async createBook(data: { title: string; author: string }) and call this.prisma.book.create({ data }).

4

Add findAll, updateBook, and deleteBook methods

In BooksService, add three async methods: findAll that returns all books using this.prisma.book.findMany(), updateBook that takes id and data to update a book using this.prisma.book.update, and deleteBook that takes id and deletes the book using this.prisma.book.delete.

NestJS

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

import { Injectable } from '@nestjs/common';
import { PrismaClient } from '@prisma/client';

@Injectable()
export class BooksService {
  private readonly prisma = new PrismaClient();

  async createBook(data: { title: string; author: string }) {
    return await this.prisma.book.create({
      data,
    });
  }

  // Add findAll, updateBook, and deleteBook methods here
  // Your code here
}

Hint

Use findMany() for findAll, update({ where: { id }, data }) for updateBook, and delete({ where: { id } }) for deleteBook.

Practice

1. In NestJS with Prisma, which method is used to retrieve multiple records from the database?

easy

A. create

B. update

C. findMany

D. delete

Solution

1. Step 1: Understand Prisma CRUD methods

   Prisma provides create to add, findMany to get multiple records, update to change, and delete to remove records.

2. Step 2: Identify method for retrieving multiple records

   The method findMany is specifically designed to fetch many records from the database.

3. Final Answer:

   findMany -> Option C

4. Quick Check:

   Retrieve multiple records = findMany [OK]

Hint: Remember: findMany fetches many records [OK]

Common Mistakes:

• Confusing create with findMany
• Using update to retrieve data
• Trying to delete to get records

2. Which of the following is the correct syntax to create a new user record using Prisma in a NestJS service?

easy

A. this.prisma.user.create({ data: { name: 'Alice' } })

B. this.prisma.user.findMany({ data: { name: 'Alice' } })

C. this.prisma.user.update({ data: { name: 'Alice' } })

D. this.prisma.user.delete({ data: { name: 'Alice' } })

Solution

1. Step 1: Identify the method to add a record

   The create method is used to add new records in Prisma.

2. Step 2: Check the syntax for creating a user

   The correct syntax is this.prisma.user.create({ data: { ... } }) where data holds the new record's fields.

3. Final Answer:

   this.prisma.user.create({ data: { name: 'Alice' } }) -> Option A

4. Quick Check:

   Create new record = create method [OK]

Hint: Use create with data object to add records [OK]

Common Mistakes:

• Using findMany instead of create
• Passing data to update without where clause
• Using delete method to add records

3. Given this Prisma update call in a NestJS service:

this.prisma.user.update({ where: { id: 5 }, data: { email: '[e-mail]' } })

What will this operation do?

medium

A. Delete the user with id 5

B. Update the email of the user with id 5 to '[e-mail]'

C. Create a new user with id 5 and email '[e-mail]'

D. Return all users with email '[e-mail]'

Solution

1. Step 1: Understand the update method parameters

   The update method requires a where clause to find the record and data to specify changes.

2. Step 2: Analyze the given call

   It targets user with id: 5 and changes the email field to '[e-mail]'.

3. Final Answer:

   Update the email of the user with id 5 to '[e-mail]' -> Option B

4. Quick Check:

   Update with where and data changes record [OK]

Hint: Update needs where to find record, data to change [OK]

Common Mistakes:

• Thinking update creates new records
• Confusing update with delete
• Missing where clause causes errors

4. What is wrong with this Prisma delete call in a NestJS service?

this.prisma.user.delete({ data: { id: 3 } })

medium

A. The delete method should use a where clause, not data

B. The delete method cannot delete by id

C. The syntax is correct and will delete user with id 3

D. The delete method requires an update object

Solution

1. Step 1: Check Prisma delete method syntax

   The delete method requires a where clause to specify which record to remove.

2. Step 2: Identify the error in the code

   The code incorrectly uses data instead of where, causing a syntax error.

3. Final Answer:

   The delete method should use a where clause, not data -> Option A

4. Quick Check:

   Delete needs where, not data [OK]

Hint: Delete uses where to find record, not data [OK]

Common Mistakes:

• Using data instead of where in delete
• Trying to update in delete method
• Omitting where clause causes errors

5. You want to update a user's name only if the user exists, otherwise create a new user with that name using Prisma in NestJS. Which approach correctly handles this logic?

hard

A. Use delete then create to replace the user

B. Call update and if it fails, call create manually

C. Use findMany then create without update

D. Use upsert with where, update, and create objects

Solution

1. Step 1: Understand Prisma's upsert method

   The upsert method updates a record if it exists or creates it if not, combining both actions safely.

2. Step 2: Identify correct usage for conditional update or create

   Using upsert with where to find the user, update for changes, and create for new record is the best practice.

3. Final Answer:

   Use upsert with where, update, and create objects -> Option D

4. Quick Check:

   Conditional update or create = upsert [OK]

Hint: Use upsert to update or create in one call [OK]

Common Mistakes:

• Manually catching update errors to create
• Using findMany without update
• Deleting before creating wastes operations