# Relationships (One-to-Many, Many-to-Many) — NestJS

Source: https://www.geekswithgeeks.com/en/nestjs/nestjs-typeorm-relationships

> Model entity relationships using TypeORM decorators.

## One-to-Many example

A User has many Posts—use `@OneToMany()` and `@ManyToOne()` decorators.

```typescript
@Entity()
export class User {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @OneToMany(() => Post, post => post.user, { cascade: true })
  posts: Post[];
}

@Entity()
export class Post {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  title: string;

  @ManyToOne(() => User, user => user.posts)
  user: User;
}
```

## Eager vs Lazy loading

By default, relations are lazy—fetch them with `leftJoinAndSelect()`. Use `eager: true` to auto-load (sparingly).