Improve self relations example

Bug description

Example in the docs suggests that self relations may be optional, but the types require the relation.

Am I missing something with the spec here? 😅

Hope the reproduction helps! 🙂

How to reproduce

datasource db {
    provider = "mysql"
    url      = env("DATABASE_URL")
}

generator client {
    provider = "prisma-client-js"
}

model User {
  id       Int      @id @default(autoincrement())
  name     String?
  husband  User      @relation("MarriagePartners", fields: [id], references: [id])
  wife     User?     @relation("MarriagePartners")
}

import { PrismaClient } from '@prisma/client'

const client = new PrismaClient()

client.user.create({
    data: {
        name: "George"
    }
})

https://github.com/maticzav/prisma-client--selfrelation-bug-reproduction

Expected behaviour

Create method should have an optional husband field.

Prisma information

Environment & setup

• OS: Mac OS
• Database: MySQL
• Prisma version:

@prisma/cli          : 2.0.0-beta.2
Current platform     : darwin
Query Engine         : query-engine 76857c35ba1e1764dd5473656ecbbb2f739e1822 (at /Users/maticzav/Code/sandbox/prisma-client-self-relation-issue/node_modules/@prisma/cli/query-engine-darwin)
Migration Engine     : migration-engine-cli 76857c35ba1e1764dd5473656ecbbb2f739e1822 (at /Users/maticzav/Code/sandbox/prisma-client-self-relation-issue/node_modules/@prisma/cli/migration-engine-darwin)
Introspection Engine : introspection-core 76857c35ba1e1764dd5473656ecbbb2f739e1822 (at /Users/maticzav/Code/sandbox/prisma-client-self-relation-issue/node_modules/@prisma/cli/introspection-engine-darwin)

• Node.js version: v12.16.1

[pantharshit00]

@maticzav No, they should not be required. We disallow required self realtions now because you can’t create a root node if they are required.

[mhwelander]

👋 Hi folks - the relations example has been updated: https://www.prisma.io/docs/reference/tools-and-interfaces/prisma-schema/relations#self-relations

(It includes example SQL that uses a unique constraint to create a 1-1 self-relation so that you can introspect.)

Thanks for raising the issue! 💚