Prisma migrations in NestJS - Step-by-Step Execution

Concept Flow - Prisma migrations

Write schema.prisma

↓

Run prisma migrate dev

↓

Migration files created

↓

Database schema updated

↓

Application uses updated schema

↓

Repeat for new changes

This flow shows how you write your Prisma schema, run migrations to update the database, and then use the updated schema in your NestJS app.

Execution Sample

NestJS

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

// Run: npx prisma migrate dev --name init

Defines a User model and runs a migration to create the corresponding database table.

Execution Table

Step	Action	Input/Command	Effect	Output/Result
1	Write schema	Add User model to schema.prisma	Schema file updated	User model defined
2	Run migration	npx prisma migrate dev --name init	Migration process starts	Migration files created
3	Apply migration	Database updated	Database schema matches User model	User table created
4	Generate client	Prisma client updated	Client reflects new schema	Client ready to use
5	Use in app	NestJS uses Prisma client	App can query User table	Data operations succeed
6	Exit	No more migrations	Process ends	Database and app in sync

💡 No more schema changes, migration process complete

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
schema.prisma	empty or old schema	User model added	User model unchanged	User model unchanged	User model unchanged	User model defined
migration files	none	none	init migration created	init migration applied	init migration applied	init migration applied
database schema	old or empty	old or empty	old or empty	User table created	User table created	User table created
Prisma client	old version	old version	old version	updated with User model	updated with User model	updated with User model

Key Moments - 2 Insights

Why do we need to run 'prisma migrate dev' after changing schema.prisma?

Because the migration command creates files and updates the database schema to match your Prisma schema. Without it, the database won't reflect your changes (see execution_table step 2 and 3).

What happens if you change schema.prisma but don't generate the Prisma client?

Your app will use an outdated client that doesn't know about new models or fields. Step 4 in the execution_table shows client generation is needed to keep the client in sync.

Visual Quiz - 3 Questions

Look at the execution_table, what is created at step 2?

A Database tables

B Migration files

C Prisma client

D NestJS modules

💡 Hint

Check the 'Effect' and 'Output/Result' columns in step 2 of the execution_table.

At which step does the database schema get updated?

A Step 3

B Step 1

C Step 4

D Step 5

💡 Hint

Look for 'Database schema matches User model' in the 'Effect' column.

If you skip step 4, what problem will you face?

A Migration files won't be created

B Database schema won't update

C Prisma client won't reflect schema changes

D NestJS app won't start

💡 Hint

Refer to the 'Prisma client' variable in variable_tracker after step 4.

Concept Snapshot

Prisma migrations let you update your database schema safely.
1. Edit schema.prisma to define models.
2. Run 'npx prisma migrate dev --name <desc>' to create migration files and update DB.
3. Prisma client regenerates to match schema.
4. Use updated client in NestJS app.
Repeat for every schema change.

Full Transcript

Prisma migrations in NestJS start by writing or updating the schema.prisma file to define your data models. Then, you run the command 'npx prisma migrate dev --name <migration_name>' which creates migration files and applies changes to your database schema. After the database updates, Prisma regenerates its client to reflect the new schema. Finally, your NestJS application uses this updated client to interact with the database. This process repeats whenever you change your data models, ensuring your database and app stay in sync.