I'm lazy

Get started with Prisma - Step 1 - Migrations

Step 1 - Migrations

2022-05-22

What's this?

Today we'll cover migrations in Prisma. We'll create a couple of models, add some data and perform respective queries. We'll extend the current schema with clients and product reviews.

Instructions

I suppose you've already read the instructions of step 0 here and you've got some response from the hello-world-like example.

If you're bored do a git fetch and switch to the step1 branch (git checkout step1), copy .env.example to .env, run yarn prisma generate and skip the next steps.

Otherwise...

First we need to create an initial migration, so let's do it: yarn prisma migrate dev --name initial-migration. This will require you to delete existing data. For convenience, I've already supplied a dump in the prisma folder, named mydb_initial.sql.
Run cat db/mydb_initial.sql | sqlite3 ./db/mydb.sqlite to reimport data.
Now let's add the Clients table. Add this to the prisma/schema.prisma file:

model Client {
  Id           Int     @id @default(autoincrement())
  ClientName String?
  ClientSurname  String?
}

Run yarn prisma migrate dev to generate the respective migration and of course generate a new @prisma/client for this application.
Now the Prisma client knows how to handle the Client table.
Now let's add the Review model and make changes to the Product and Client models. Add these lines to the prisma/schema.prisma file:

model Review {
  grade        Int
  clientId     Int
  productId    Int
  client     Client        @relation(fields: [clientId], references: [Id])
  product     Product        @relation(fields: [productId], references: [Id])
  @@id([clientId, productId])
}

Change Client as shown below:

model Client {
  Id           Int     @id @default(autoincrement())
  ClientName String?
  ClientSurname  String?
  Review       Review[]
}

Change Product as follows:

model Product {
  Id              Int     @id @default(autoincrement())
  ProductName     String?
  SupplierId      Int
  CategoryId      Int
  QuantityPerUnit String?
  UnitPrice       Decimal
  UnitsInStock    Int
  UnitsOnOrder    Int
  ReorderLevel    Int
  Discontinued    Int
  Review          Review[]
}

Run yarn prisma migrate dev --name add-reviews, check the new migration that was made inside prisma/migrations.
Now the Prisma client knows how to handle the updated Client and Product models and their M:N relation through the Review model.

What I can do next?

Run yarn prisma studio to start Prisma Studio and check the changes. Add some clients and some reviews.
Run yarn tsc ./src/index.ts and then node dist/index.js to see the Clients and the Reviews table on the console.
Play around and have fun with the src/step1.ts