author.entity.ts

@Entity('tblCategory')
export class Category {
  @PrimaryColumn({ name: 'ID_CATEGORY', type: 'uniqueidentifier' })
  id: string;
  
  @Column({ name: 'NM_CATEGORY', type: 'nvarchar' })
  name: string;

  @OneToMany(type => Book, book => book.category)
  @JoinTable({
    name: 'tblBook',
    joinColumn: { name: 'ID_BOOK' },
    inverseJoinColumn: { name: 'ID_CATEGORY' },
  })
  books: Book[];

}

book.entity.ts

@Entity('tblBook')
export class Book {
  @PrimaryColumn({ name: 'ID_BOOK', type: 'uniqueidentifier' })
  id: string;
  
  @Column({ name: 'DS_TITLE', type: 'nvarchar' })
  title: string;

  @Column({ name: 'DS_SUBTITILE', type: 'nvarchar' })
  subtitle: string;

  @ManyToOne(() => Category, m => m.books)
  @JoinColumn({ name: 'ID_CATEGORY' })
  category: Category;
}

category.service.ts

import { Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository, MoreThanOrEqual, Equal } from 'typeorm';
import { Category } from './category.entity';

@Injectable()
export class ForragemPastoService {
  constructor(
    @InjectRepository(Category)
    private readonly repository: Repository<Category>,
  ) {}

  async save(category: Category): Promise<Category> {
    await this.repository.save(category);
    const data = await this.repository.findOne(category.id, {
      relations: ['books'],
    });
    return data;
  }
}