Can bidirectional one-to-one relationship have null on non-foreign-key-owning side?

Issue type:

[x] question

Database system/driver:

[x] postgres

I have a one to one relationship like so:

@Entity()
export class Car extends BaseEntity {
	@PrimaryColumn()
	id: number

	@OneToOne(type => User, user => user.car, { nullable: true })
	user?: User
}

@Entity()
export class User extends BaseEntity {
	@PrimaryGeneratedColumn()
	id: number

	@OneToOne(type => Car, car => car.user)
	@JoinColumn()
	car: Car
}

Is it okay for me to able to create Users without creating Cars, and Cars without Users? By making car.user nullable, I’m wanting to make it such that a car can exist without a user, but a user cannot exist without a car.

[mantagen]

@saoudrizwan

You’ve probably moved on from that particular problem, but if you haven’t or if anyone stumbles on this:

The OneToOne column will be nullable by default. No make it not nullable, see this comment: https://github.com/typeorm/typeorm/issues/4301#issuecomment-634032714

For you it would look something like (EDIT: this code snippet contains an error, see https://github.com/typeorm/typeorm/issues/4553#issuecomment-726717067 for correction)

@Entity()
export class Car extends BaseEntity {
	@PrimaryColumn()
	id: number

	@OneToOne(type => User, user => user.car)
	user: User | null
}
@Entity()
export class User extends BaseEntity {
	@PrimaryGeneratedColumn()
	id: number

        @Column({ type: "integer" })
        userId: number;
        
	@OneToOne(type => Car, car => car.user)
	@JoinColumn()
	car: Car
}

By adding userId, which defaults to nullable: false, a NOT NULL constraint will be added to the userId field in the Car table (which will not be added in your example as you’ve written it)

[mantagen]

@msiric if you want this behaviour then I recommend that you follow the docs here: https://github.com/typeorm/typeorm/blob/master/docs/one-to-one-relations.md

That should give you the behaviour that you want to achieve.

This thread is specifically for adding a “NOT_NULL” constraint to user.carId, which I don’t think is compatible with the way you’re wanting to insert data. I could be wrong.

For other questions, please check out the community slack or check TypeORM’s documentation page on other support avenues - cheers!