model City {
  id                    String    @id() @unique() @map("city_code_alphabet_3") @db.VarChar(3)

  // Relationships
  ArticleForDestination Article[]     @relation(name: "articleForDestination")
  ArticleForOrigin      Article[]     @relation(name: "articleForOrigin")

  @@map("cities")
}

model Article {
  id          Int          @id @default(autoincrement())
  createdAt   DateTime     @default(now()) @map("created_at") @db.Timestamptz(0)
  updatedAt   DateTime?    @updatedAt @map("updated_at") @db.Timestamptz(0)

  // Relationships
  destinationCityId String @map("destination_city_id")
  Destination       City   @relation(name: "articleForDestination", fields: [destinationCityId], references: [id])
  originCityId      String @map("origin_city_id")
  Origin            City   @relation(name: "articleForOrigin", fields: [originCityId], references: [id])

  @@index([destinationCityId, originCityId])
  @@map("article")
}

Problem: I can insert multiple record with the same

destinationCityId

and

originCityId

? What is wrong?