How to create self relation in entity?

Question

I have entity file:

@Entity('groups')
export class Groups {
  @PrimaryGeneratedColumn({ type: 'integer', name: 'id' })
  id: number;

  @Column({ type: 'int', nullable: true })
  parentid: number | null;

  @Column({ type: 'varchar', length: 1024 })
  name: string;

  @Column({ type: 'varchar', nullable: true, length: 4096 })
  description?: string;
}

and I want to parentid will be have foreign key to id, like on this image:

May be someone know how I can do that?

Thanks for answers.

Answer 1

Based on this link, there are multiple ways to do that but personally I suggest you this:

@Entity('groups')
export class Groups {
  @PrimaryGeneratedColumn({ type: 'integer', name: 'id' })
  id: number;

  @Column({ type: 'varchar', length: 1024 })
  name: string;

  @Column({ type: 'varchar', nullable: true, length: 4096 })
  description?: string;

  @Column({ nullable: true })
  parentId: number;

  @ManyToOne((type) => Groups, (groups) => groups.children)
  @JoinColumn({ name: 'parentId' })
  parent: Groups;

  @OneToMany((type) => Groups, (groups) => groups.parent)
  children: Groups[];
}