Prisma migrations in NestJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens after running prisma migrate dev in a NestJS project?

You run prisma migrate dev in your NestJS project. What is the immediate effect on your database and Prisma client?

A It applies all existing migrations to the database but does not create new migration files.

B It only creates a migration file but does not apply it to the database or update the Prisma client.

C It creates a new migration file, applies it to the database, and updates the Prisma client automatically.

D It updates the Prisma client without creating migration files or changing the database.

💡 Hint

Think about what prisma migrate dev does during development to keep your database and client in sync.

The prisma migrate dev command creates a new migration file based on your Prisma schema changes, applies it to your database, and regenerates the Prisma client so your code can use the updated schema.

📝 Syntax

intermediate

Which Prisma schema snippet correctly defines a new model for migration?

You want to add a new model Post with an id as primary key and a title field. Which schema snippet is correct for Prisma migrations?

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

B model Post { id Int primaryKey title String }

C model Post { id Int @primary @autoIncrement title String }

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

💡 Hint

Look for the correct Prisma attributes for primary key and auto-increment.

Prisma uses @id to mark the primary key and @default(autoincrement()) to auto-increment integer IDs. Option A uses the correct syntax.

🔧 Debug

advanced

Why does prisma migrate deploy fail with 'Migration not found' error?

You deployed your NestJS app and ran prisma migrate deploy on production, but it fails with 'Migration not found' error. What is the most likely cause?

A The database URL in <code>.env</code> is incorrect and points to a wrong database.

B The Prisma schema file has syntax errors preventing migration deployment.

C The Prisma client was not regenerated after schema changes.

D The migration files were not pushed to the production server or are missing in the migrations folder.

💡 Hint

Consider what prisma migrate deploy expects to find on the server.

prisma migrate deploy applies existing migration files to the database. If the migration files are missing or not copied to production, it cannot find them and throws this error.

❓ state_output

advanced

What is the state of the database after running prisma migrate reset?

You run prisma migrate reset in your NestJS project. What happens to your database?

A The database is dropped, recreated, all migrations are applied fresh, and the Prisma client is regenerated.

B Only the last migration is rolled back, and the database keeps previous data.

C The database schema is updated without dropping data, applying only new migrations.

D The Prisma client is regenerated without changing the database.

💡 Hint

Think about what 'reset' means for a database in development.

prisma migrate reset drops the database, recreates it, applies all migrations from scratch, and regenerates the Prisma client. This clears all data and schema changes.

🧠 Conceptual

expert

Why should you avoid running prisma migrate dev directly on production?

In a NestJS project, why is it recommended to use prisma migrate deploy instead of prisma migrate dev on production environments?

A <code>prisma migrate dev</code> does not apply migrations to the database, so production schema stays outdated.

B <code>prisma migrate dev</code> may create new migration files and prompt for user input, which is unsafe in production automation.

C <code>prisma migrate dev</code> only works with SQLite databases, not production databases like PostgreSQL.

D <code>prisma migrate dev</code> automatically deletes all data in production databases.

💡 Hint

Consider the differences in behavior and safety between development and production migration commands.

prisma migrate dev is designed for development. It can create new migration files and interactively prompt users, which can cause issues in automated production environments. prisma migrate deploy safely applies existing migrations without prompts.