CRUD operations with Prisma in NextJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Prisma create operation in Next.js?

Consider this Next.js API route using Prisma to create a new user:

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

export default async function handler(req, res) {
  if (req.method === 'POST') {
    const user = await prisma.user.create({
      data: { name: 'Alice', email: '[e-mail]' }
    });
    res.json(user);
  } else {
    res.status(405).end();
  }
}

What will the response JSON contain after a successful POST request?

NextJS

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

export default async function handler(req, res) {
  if (req.method === 'POST') {
    const user = await prisma.user.create({
      data: { name: 'Alice', email: '[e-mail]' }
    });
    res.json(user);
  } else {
    res.status(405).end();
  }
}

A {"name": "Alice", "email": "[e-mail]"}

B {"error": "Method not allowed"}

C {"id": 1, "name": "Alice", "email": "[e-mail]"}

D {"message": "User created successfully"}

💡 Hint

Prisma returns the full created record including the auto-generated ID.

The prisma.user.create method returns the full user object including the auto-generated id. So the response JSON includes id, name, and email.

❓ state_output

intermediate

What is the result of this Prisma update operation?

Given this Prisma update code snippet in a Next.js API route:

const updatedUser = await prisma.user.update({
  where: { id: 5 },
  data: { email: '[e-mail]' }
});
console.log(updatedUser);

Assuming a user with id = 5 exists, what will console.log(updatedUser) output?

NextJS

const updatedUser = await prisma.user.update({
  where: { id: 5 },
  data: { email: '[e-mail]' }
});
console.log(updatedUser);

A {"id": 5, "name": "Existing Name", "email": "[e-mail]"}

B {"id": 5, "email": "[e-mail]"}

C undefined

D Throws Prisma.PrismaClientKnownRequestError

💡 Hint

The update method returns the full updated record.

The prisma.user.update method returns the entire updated user object, including unchanged fields like name. So the output includes id, name, and the updated email.

🔧 Debug

advanced

Why does this Prisma delete operation cause an error?

Review this Next.js API route snippet:

export default async function handler(req, res) {
  if (req.method === 'DELETE') {
    const deletedUser = await prisma.user.delete({
      where: { email: '[e-mail]' }
    });
    res.json(deletedUser);
  } else {
    res.status(405).end();
  }
}

What error will this code throw if no user has the given email?

NextJS

const deletedUser = await prisma.user.delete({
  where: { email: '[e-mail]' }
});

A No error, returns null

B TypeError: Cannot read property 'email' of undefined

C SyntaxError: Unexpected token delete

D Prisma.PrismaClientKnownRequestError: Record to delete does not exist.

💡 Hint

Deleting a non-existing record causes a specific Prisma error.

Prisma throws PrismaClientKnownRequestError when trying to delete a record that does not exist, indicating the record to delete was not found.

🧠 Conceptual

advanced

Which Prisma query returns all users with emails ending in '.org'?

Choose the Prisma query that correctly fetches all users whose email ends with '.org'.

A prisma.user.findMany({ where: { email: { endsWith: '.org' } } })

B prisma.user.findMany({ where: { email: { contains: '.org' } } })

C prisma.user.findMany({ where: { email: { startsWith: '.org' } } })

D prisma.user.findMany({ where: { email: { equals: '.org' } } })

💡 Hint

Look for the operator that matches the end of a string.

The endsWith operator filters strings that end with the specified substring. contains matches anywhere, startsWith matches the beginning, and equals matches exact strings.

📝 Syntax

expert

What error does this Prisma upsert code produce?

Analyze this Prisma upsert code snippet:

await prisma.user.upsert({
  where: { id: 10 },
  update: { name: 'Bob' },
  create: { email: '[e-mail]' }
});

What error will this code raise?

NextJS

await prisma.user.upsert({
  where: { id: 10 },
  update: { name: 'Bob' },
  create: { email: '[e-mail]' }
});

A SyntaxError: Unexpected token 'await'

B Prisma.PrismaClientValidationError: Missing required field 'name' in create data.

C No error, operation succeeds

D Prisma.PrismaClientKnownRequestError: Unique constraint failed on the fields: (`id`)

💡 Hint

Check if the create data includes all required fields.

The create object is missing the required name field, causing a validation error. Prisma requires all non-nullable fields in create data.

Practice

1. What does the prisma.user.create() method do in Next.js with Prisma?

easy

A. It adds a new user record to the database.

B. It fetches all user records from the database.

C. It updates an existing user record.

D. It deletes a user record from the database.

Solution

1. Step 1: Understand the method name

   The method create() is used to add new data in Prisma.

2. Step 2: Match method to CRUD operation

   Creating means adding new records, so prisma.user.create() adds a new user.

3. Final Answer:

   It adds a new user record to the database. -> Option A

4. Quick Check:

   Create method = Add new record [OK]

Hint: Create method adds new data, not read or delete [OK]

Common Mistakes:

• Confusing create() with findMany() which reads data
• Thinking create() updates existing records
• Assuming create() deletes records

2. Which of the following is the correct syntax to update a user with id 5 using Prisma in Next.js?

easy

A. prisma.user.edit({ where: { id: 5 }, data: { name: 'Alice' } })

B. prisma.user.modify({ id: 5, name: 'Alice' })

C. prisma.user.update({ where: { id: 5 }, data: { name: 'Alice' } })

D. prisma.user.change({ id: 5, data: { name: 'Alice' } })

Solution

1. Step 1: Identify Prisma update syntax

   Prisma uses update() with where and data keys to update records.

2. Step 2: Check option correctness

   Only prisma.user.update({ where: { id: 5 }, data: { name: 'Alice' } }) uses correct method update() and proper keys where and data.

3. Final Answer:

   prisma.user.update({ where: { id: 5 }, data: { name: 'Alice' } }) -> Option C

4. Quick Check:

   Update method uses where and data keys [OK]

Hint: Update uses update({ where, data }) syntax [OK]

Common Mistakes:

• Using non-existent methods like modify(), change(), edit()
• Missing where or data keys in update()
• Passing id directly without where object

3. Given this code snippet in Next.js with Prisma:

const users = await prisma.user.findMany({ where: { active: true } });
console.log(users.length);

What will console.log(users.length) output?

medium

A. Always 0, because findMany returns undefined.

B. The total number of users, active or not.

C. An error because findMany needs data key.

D. The number of active users in the database.

Solution

1. Step 1: Understand findMany with where filter

   The findMany() method returns an array of records matching the where condition.

2. Step 2: Analyze the filter condition

   Only users with active: true are returned, so users.length is count of active users.

3. Final Answer:

   The number of active users in the database. -> Option D

4. Quick Check:

   findMany with where returns filtered array [OK]

Hint: findMany returns array; length counts filtered records [OK]

Common Mistakes:

• Thinking findMany returns undefined or error
• Ignoring the where filter effect
• Assuming it returns all users without filter

4. Identify the error in this Prisma delete operation:

await prisma.user.delete({ id: 10 });

medium

A. Missing the 'where' key wrapping the id.

B. Using delete() instead of remove().

C. id should be a string, not a number.

D. delete() cannot be used with await.

Solution

1. Step 1: Check delete() method syntax

   Prisma's delete() requires an object with a where key specifying the record to delete.

2. Step 2: Identify missing where key

   The code passes { id: 10 } directly, missing where: { id: 10 }.

3. Final Answer:

   Missing the 'where' key wrapping the id. -> Option A

4. Quick Check:

   Delete needs where key with id [OK]

Hint: Delete needs where: { id } object, not just id [OK]

Common Mistakes:

• Omitting where key in delete()
• Using remove() which does not exist in Prisma
• Thinking id type must be string always
• Believing delete() can't be awaited

5. You want to update a user's email only if the user exists, otherwise create a new user with that email. Which Prisma method best fits this use case in Next.js?

hard

A. prisma.user.create({ data: { email } })

B. prisma.user.upsert({ where: { email }, update: { email }, create: { email } })

C. prisma.user.update({ where: { email }, data: { email } })

D. prisma.user.findUnique({ where: { email } })

Solution

1. Step 1: Understand the upsert method

   Upsert updates if record exists, else creates new one in Prisma.

2. Step 2: Match use case to method

   Since we want to update or create based on existence, upsert() fits perfectly.

3. Final Answer:

   prisma.user.upsert({ where: { email }, update: { email }, create: { email } }) -> Option B

4. Quick Check:

   Upsert = update or create [OK]

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

Common Mistakes:

• Using update() alone which fails if user missing
• Using create() alone which fails if user exists
• Using findUnique() which only reads data