Setting up your Database

To see this in action, first create a blog database with 2 collections: User and Post. We recommend MongoDB Compass for setting this up:

First, add a user to our User collection:

Next, add some posts to our Post collection. It's important that the ObjectID in userId matches the user you created above.

Initializing Prisma

Now that you have a MongoDB database, the next step is to create a new project and initialize Prisma:

mkdir blog
cd blog
npm init -y
npm install -D prisma
npx prisma init

Initializing Prisma will create a prisma/schema.prisma file. Edit this file to use MongoDB:

prisma/schema.prisma
1datasource db {
2  provider = "mongodb"
3  url      = env("DATABASE_URL")
4}
5
6generator client {
7  provider = "prisma-client-js"
8}

Next you'll need to adjust your .env file to point the DATABASE_URL to your MongoDB database

Introspecting MongoDB with Prisma

You're now ready to introspect. Run the following command to introspect your database:

npx prisma db pull

This command introspects our database and writes the inferred schema into your prisma/schema.prisma file:

prisma/schema.prisma
1datasource db {
2  provider = "mongodb"
3  url      = env("DATABASE_URL")
4}
5
6generator client {
7  provider = "prisma-client-js"
8}
9
10model Post {
11  id     String @id @default(auto()) @map("_id") @db.ObjectId
12  title  String
13  userId String @db.ObjectId
14}
15
16model User {
17  id    String @id @default(auto()) @map("_id") @db.ObjectId
18  email String
19}

Tweaking the Schema

To be able to join data using Prisma Client, you can add the @relation attributes to our models:

prisma/schema.prisma
1datasource db {
2  provider = "mongodb"
3  url      = env("DATABASE_URL")
4}
5
6generator client {
7  provider = "prisma-client-js"
8}
9
10model Post {
11  id     String @id @default(auto()) @map("_id") @db.ObjectId
12  title  String
13  userId String @db.ObjectId
+  user   User   @relation(fields: [userId], references: [id])
15}
16
17model User {
18  id    String @id @default(auto()) @map("_id") @db.ObjectId
19  email String
+  posts Post[]
21}

And with that, you're ready to generate Prisma Client.