Database migrations in NextJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new migration file using Prisma CLI.

NextJS

npx prisma migrate [1] --name init

Drag options to blanks, or click blank then click option'

Arun

Bsave

Cgenerate

Dcreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'run' instead of 'create' to make a migration file.

Confusing 'save' or 'generate' with migration commands.

Use create to make a new migration file with Prisma.

2fill in blank

medium

Complete the code to apply all pending migrations to the database.

NextJS

npx prisma migrate [1]

Drag options to blanks, or click blank then click option'

Adev

Bdeploy

Cdeployments

Dcreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'create' instead of 'deploy' to apply migrations.

Trying 'deployments' which is not a valid command.

The deploy command applies all pending migrations to the database.

3fill in blank

hard

Fix the error in the migration command to reset the database and apply migrations.

NextJS

npx prisma migrate [1] --force

Drag options to blanks, or click blank then click option'

Asave

Bdeploy

Creset

Dcreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'deploy' or 'create' instead of 'reset' to reset the database.

Forgetting the '--force' flag when resetting.

The reset command resets the database and reapplies migrations.

4fill in blank

hard

Fill both blanks to write a Prisma schema model with an auto-incrementing ID and a string field.

NextJS

model User {
  id   Int    @id @default([1]())
  name String @[2]
}

Drag options to blanks, or click blank then click option'

Adefault

Bunique

Cautoincrement

Drequired

Attempts:

3 left

💡 Hint

Common Mistakes

Using '@default' instead of '@autoincrement' for ID.

Using '@required' which is not a Prisma decorator.

The @default(autoincrement()) decorator makes the ID auto-increment. The @unique decorator ensures the name is unique.

5fill in blank

hard

Fill all three blanks to write a migration script that creates a table with a primary key and a timestamp.

NextJS

CREATE TABLE [1] (
  id SERIAL PRIMARY KEY,
  created_at [2] DEFAULT [3]
);

Drag options to blanks, or click blank then click option'

Ausers

BTIMESTAMP

CCURRENT_TIMESTAMP

DVARCHAR(255)

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong data types for timestamp.

Forgetting to set default value for created_at.

This SQL creates a users table with an auto-incrementing id and a created_at timestamp defaulting to the current time.

Practice

1.

What is the main purpose of database migrations in a Next.js project?

easy

A. To deploy the Next.js app to the server

B. To safely update the database structure as the app evolves

C. To create user interfaces automatically

D. To write CSS styles for the app

Solution

1. Step 1: Understand database migrations

   Database migrations are used to change the database schema safely without losing data.

2. Step 2: Relate to Next.js usage

   In Next.js, migrations help keep the database structure in sync with app changes.

3. Final Answer:

   To safely update the database structure as the app evolves -> Option B

4. Quick Check:

   Database migrations = safe schema updates [OK]

Hint: Migrations change database structure safely [OK]

Common Mistakes:

• Confusing migrations with UI or styling tasks
• Thinking migrations deploy the app
• Assuming migrations create app features

2.

Which command is used to create and apply a new migration in a Next.js project using Prisma?

?

easy

A. next dev

B. npm run build

C. npx prisma migrate dev

D. npx prisma generate

Solution

1. Step 1: Identify Prisma migration command

   The command npx prisma migrate dev creates and applies migrations during development.

2. Step 2: Differentiate from other commands

   npm run build builds the app, next dev runs dev server, and npx prisma generate regenerates Prisma client but does not migrate.

3. Final Answer:

   npx prisma migrate dev -> Option C

4. Quick Check:

   Migration command = npx prisma migrate dev [OK]

Hint: Use 'npx prisma migrate dev' to create and apply migrations [OK]

Common Mistakes:

• Using 'npm run build' to migrate database
• Confusing 'npx prisma generate' with migration
• Running 'next dev' expecting migration

3.

Given this Prisma schema change and migration command, what will happen?

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

// After adding a new field:
model User {
  id       Int    @id @default(autoincrement())
  email    String @unique
  name     String?
  isActive Boolean @default(true)
}

Command: npx prisma migrate dev --name add-isActive

medium

A. A new migration file is created and applied adding the isActive column with default true

B. The migration fails because isActive is missing in existing rows

C. The database schema remains unchanged

D. The app crashes due to schema mismatch

Solution

1. Step 1: Understand schema change

   A new Boolean field isActive with default true is added to the User model.

2. Step 2: Effect of migration command

   The command creates a migration file that adds the new column with default value, so existing rows get true automatically.

3. Final Answer:

   A new migration file is created and applied adding the isActive column with default true -> Option A

4. Quick Check:

   Adding field with default = migration applies safely [OK]

Hint: Adding field with default creates migration safely [OK]

Common Mistakes:

• Thinking migration fails due to missing data for new field
• Assuming schema does not change without manual SQL
• Believing app crashes immediately after migration

4.

What is wrong with this migration command usage in a Next.js project?

npx prisma migrate dev --name

medium

A. The command is correct and will run successfully

B. The command should be run with npm, not npx

C. The command should be prisma migrate deploy instead

D. The migration name is missing after --name flag

Solution

1. Step 1: Check command syntax

   The --name flag requires a migration name string after it.

2. Step 2: Identify missing argument

   Here, no name is provided, so the command will error out.

3. Final Answer:

   The migration name is missing after --name flag -> Option D

4. Quick Check:

   Migration name required after --name [OK]

Hint: Always provide a name after --name flag [OK]

Common Mistakes:

• Omitting migration name after --name
• Confusing migrate dev with migrate deploy
• Using npm instead of npx unnecessarily

5.

You want to add a new required field age Int to your User model in Prisma, but your database already has users without this field. What is the best way to handle this migration?

hard

A. Add age Int? as optional first, migrate, then backfill data, then make it required

B. Add age Int directly and run migration; it will succeed automatically

C. Delete all existing users before migration to avoid errors

D. Skip migration and add the field only in the app code

Solution

1. Step 1: Understand required field constraints

   Adding a required field age Int directly will fail because existing rows lack this data.

2. Step 2: Use a safe migration approach

   First add the field as optional (age Int?), migrate, then update existing data, and finally change it to required.

3. Final Answer:

   Add age Int? as optional first, migrate, then backfill data, then make it required -> Option A

4. Quick Check:

   Make new required fields optional first [OK]

Hint: Add new required fields as optional first [OK]

Common Mistakes:

• Adding required field directly causing migration failure
• Deleting data unnecessarily
• Skipping migration and causing runtime errors