Prisma Migration example with TypeScript

This example shows how to use Prisma Client in a simple TypeScript script to read and write data in a SQLite database. You can find the database file with some dummy data at ./prisma/dev.db.

important notes:

• You should never edit your schemas in your db table editor. Every change for the tables should be done in prisma.schema. Otherwise migration history won't match and going to require hard reset for db which is we do not want to experience. npx prisma db pull should be only used on eding prisma to existing project that has a db.

• npx prisma migrate deploy should be run in CI pipeline like github actions. You can also add into build step of your own CI.

• If you are working with MongoDb, you have to use npx prisma db push instead of npx migrate dev .

Getting started

1. Download example and install dependencies

Clone this example:

git clone [email protected]:furkanksl/prisma-migration-tutorial.git

Install npm dependencies:

cd prisma-migration-tutorial
npm install

2. Create the database

Run the following command to create your SQLite database file. This also creates the User and Post tables that are defined in prisma/schema.prisma:

npx prisma migrate dev --name init

3. Run the script

Let's add dummy data into db. Execute the script with this command:

npm run dev

Evolving the app

Evolving the application typically requires two steps:

1. Migrate your database using Prisma Migrate
2. Update your application code

For the following example scenario, assume you want to add a "profile" feature to the app where users can create a profile and write a short bio about themselves.

1. Migrate your database using Prisma Migrate

The first step is to add a new table, e.g. called Profile, to the database. You can do this by adding a new model to your Prisma schema file file and then running a migration afterwards:

// schema.prisma

model Post {
  id        Int     @default(autoincrement()) @id
  title     String
  content   String?
  published Boolean @default(false)
  author    User?   @relation(fields: [authorId], references: [id])
  authorId  Int
}

model User {
  id      Int      @default(autoincrement()) @id
  name    String?
  email   String   @unique
  posts   Post[]
+ postComments PostComment[]
}

+model PostComment {
+  id        Int     @id @default(autoincrement())
+  content   String?
+  post      Post?   @relation(fields: [postId], references: [id])
+  postId    Int?
+}

Once you've updated your data model, you can execute the changes against your database with the following command:

npx prisma migrate dev

2. Update your application code

You can now use your PrismaClient instance to perform operations against the new PostComment table.

3. Push your schema changes to production

You should run this command in a CI pipeline like github actions. You can also add into build step of your own CI.

npx prisma migrate deploy

4. Rollback ( for down migrations )

To be able to rollback when you have down migration (failed migration), Prisma provides you a npx prisma migrate diff. This step should be done before you create a new migration.

npx prisma migrate diff \
 --from-schema-datamodel prisma/schema.prisma \
 --to-schema-datasource prisma/schema.prisma \
 --script > down.sql

You can put that down.sql file into last successfull migration's folder in prisma/migrations by manual or just giving a path in command above.

Basically, down.sql file will include whats changed from last migration.

By running this command, you are able to rollback to last migration if your current migration has failed.

npx prisma migrate resolve --rolled-back 20240424114840_add_createdat_field_in_post_comment_table

5. If you already experience the db reset issue, you can set baseline of migrations with commands below:

mkdir -p prisma/migrations/0_init

npx prisma migrate diff \
--from-empty \
--to-schema-datamodel prisma/schema.prisma \
--script > prisma/migrations/0_init/migration.sql

npx prisma migrate resolve --applied 0_init

Baselining

Switch to another database (e.g. PostgreSQL, MySQL, SQL Server, MongoDB)

If you want to try this example with another database than SQLite, you can adjust the the database connection in prisma/schema.prisma by reconfiguring the datasource block.

Learn more about the different connection configurations in the docs.

Expand for an overview of example configurations with different databases

PostgreSQL

For PostgreSQL, the connection URL has the following structure:

datasource db {
  provider = "postgresql"
  url      = "postgresql://USER:PASSWORD@HOST:PORT/DATABASE?schema=SCHEMA"
}

Here is an example connection string with a local PostgreSQL database:

datasource db {
  provider = "postgresql"
  url      = "postgresql://janedoe:mypassword@localhost:5432/notesapi?schema=public"
}

MySQL

For MySQL, the connection URL has the following structure:

datasource db {
  provider = "mysql"
  url      = "mysql://USER:PASSWORD@HOST:PORT/DATABASE"
}

Here is an example connection string with a local MySQL database:

datasource db {
  provider = "mysql"
  url      = "mysql://janedoe:mypassword@localhost:3306/notesapi"
}

Microsoft SQL Server

Here is an example connection string with a local Microsoft SQL Server database:

datasource db {
  provider = "sqlserver"
  url      = "sqlserver://localhost:1433;initial catalog=sample;user=sa;password=mypassword;"
}

MongoDB

Here is an example connection string with a local MongoDB database:

datasource db {
  provider = "mongodb"
  url      = "mongodb://USERNAME:PASSWORD@HOST/DATABASE?authSource=admin&retryWrites=true&w=majority"
}

• Check out the Prisma docs