I want to use FK as id（as a composite key）

[duri0214]

Problem

When I set a composite key that includes FK as an ID, the ID violates the unique key.
Even if you create a composite key, a unique constraint is created on the FK, so duplicate FKs are not allowed.
I think it is possible to have a composite key like this in business.

classDiagram
  class areas {
     id: INT
     name: string
  }
  class weather_forecast {
      date: Date
     temperature: INT
     area_id: FK
  }
  weather_forecast --> areas : areas_id

CREATE TABLE `weather_forecasts` (
  `areas_id` VARCHAR(191) NOT NULL,
  `date` VARCHAR(191) NOT NULL,
  `temperature` INTEGER NOT NULL,
  `created_at` DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
  `updated_at` DATETIME(3) NULL,
  
  UNIQUE INDEX `weather_forecasts_areas_id_key` (`areas_id`),
  UNIQUE INDEX `weather_forecasts_areas_id_date_key` (`areas_id`, `date`)
) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Suggested solution

Ability to create a composite key of date and xxx_id

Alternatives

Additional context

[janpio]

What is the Prisma context of your question? What Prisma schema do you get when you introspect your database that has that behavior?

(Aside: The SQL you are sharing does not show any foreign key, so does not match the ERD or the issue title)

[duri0214]

thank you for response :)
This is what it looks like when written in prisma schema.

model Areas {
  id String @id
  name String
  weatherForecasts WeatherForecasts[]
}
model WeatherForecasts{
  areas Areas @relation(fields: [areasId], references: [id], onDelete: Cascade)
  areasId String @unique @map("areas_id")
  date String
  temperature: Int
  createdAt DateTime @default(now()) @map("created_at")
  updatedAt DateTime? @updateAt @map("updated_at")
}

@@unique([date, areasId])
@@map("weather_forecasts")

[janpio]

That is not a valid Prisma schema (for multiple reasons, we do not support : after the field name and no @@unique or @@map outside of models).

Can you please clarify your issue or question? Thanks.