Handle multiple databases with Prisma

We can use the Prisma ORM to access multiple database in the same project. Here we will see how to do it.

1. Create a new Prisma file

Make a new folder where the schema.prisma file will live. It can be created using the Prisma init command.

prisma init

This will create the Prisma schema file inside a prisma/ directory. You can also make the Prisma schema manually if you want to have a different folder structure.

Note: If you want to pull the state of a database to the new schema.prisma file, you have to specify the path to that prisma file.

prisma db pull --schema ./path/to/schema.prisma

2. Specify where the Prisma client of the second database will be generated

By default, when a Prisma client is generated, Prisma creates a .prisma/ folder inside the node_modules/. And this client is invoked by the @prisma/client package.

To access the second database through Prisma, we need to generate the Prisma client in a directory different than the default one. To do this, add an output property in the generate section of the Prisma schema file to specify where the Prisma client for this schema wil be generated.

generator client {
	provider = "prisma-client-js"
	output = "../../node_modules/@prisma-second-db"
}

3. Generate the Prisma client

Now we need to generate the Prisma client, make sure to specify the path to the Prisma schema file, otherwise, Prisma will generate the client of the default database.

prisma generate --schema ./path/to/schema.prisma

Note: You can also generate and apply database migrations to the second database.

prisma migrate dev --schema ./path/to/schema.prisma

4. Import the Prisma client from the specified output folder

Finally, we can import the Prisma client directly from the folder where we generated it. In this example, the Prisma client was generated inside the node_modules/, so we can just import it from there:

import { PrismaClient } from "@prisma-second-db";