Relations (OneToMany, ManyToOne, ManyToMany) in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a OneToMany relation from User to Post.

NestJS

import { Entity, PrimaryGeneratedColumn, Column, [1] } from 'typeorm';

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

  @Column()
  name: string;

  @[1](() => Post, post => post.user)
  posts: Post[];
}

Drag options to blanks, or click blank then click option'

AJoinColumn

BManyToOne

CManyToMany

DOneToMany

Attempts:

3 left

💡 Hint

Common Mistakes

Using ManyToOne instead of OneToMany here.

Forgetting to import the decorator.

The OneToMany decorator defines a one-to-many relation from User to Post.

2fill in blank

medium

Complete the code to define the ManyToOne side of the relation from Post to User.

NestJS

import { Entity, PrimaryGeneratedColumn, Column, [1] } from 'typeorm';

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

  @Column()
  title: string;

  @[1](() => User, user => user.posts)
  user: User;
}

Drag options to blanks, or click blank then click option'

AManyToOne

BOneToMany

CManyToMany

DJoinTable

Attempts:

3 left

💡 Hint

Common Mistakes

Using OneToMany on the Post side.

Confusing JoinTable with JoinColumn.

The ManyToOne decorator defines the many-to-one side from Post to User.

3fill in blank

hard

Fix the error in the ManyToMany relation between Student and Course by completing the decorator.

NestJS

import { Entity, PrimaryGeneratedColumn, Column, [1] } from 'typeorm';

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

  @Column()
  name: string;

  @[1](() => Course, course => course.students)
  courses: Course[];
}

Drag options to blanks, or click blank then click option'

AOneToMany

BManyToMany

CManyToOne

DJoinColumn

Attempts:

3 left

💡 Hint

Common Mistakes

Using OneToMany or ManyToOne instead of ManyToMany.

Forgetting to add JoinTable on one side.

The ManyToMany decorator is used to define many-to-many relations like between Student and Course.

4fill in blank

hard

Fill both blanks to complete the ManyToMany relation with JoinTable between Course and Student.

NestJS

import { Entity, PrimaryGeneratedColumn, Column, [1], [2] } from 'typeorm';

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

  @Column()
  title: string;

  @ManyToMany(() => Student, student => student.courses)
  @[2]()
  students: Student[];
}

Drag options to blanks, or click blank then click option'

AManyToMany

BJoinTable

COneToMany

DJoinColumn

Attempts:

3 left

💡 Hint

Common Mistakes

Using JoinColumn instead of JoinTable.

Not importing both decorators.

The ManyToMany decorator defines the relation, and JoinTable creates the join table in the database.

5fill in blank

hard

Fill all three blanks to create a OneToMany and ManyToOne relation between Author and Book with proper imports and decorators.

NestJS

import { Entity, PrimaryGeneratedColumn, Column, [1], [2], [3] } from 'typeorm';

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

  @Column()
  name: string;

  @[2](() => Book, book => book.author)
  books: Book[];
}

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

  @Column()
  title: string;

  @[3](() => Author, author => author.books)
  author: Author;
}

Drag options to blanks, or click blank then click option'

AOneToMany

BManyToOne

CJoinColumn

DManyToMany

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up OneToMany and ManyToOne decorators.

Forgetting to import all needed decorators.

Import OneToMany, ManyToOne, and JoinColumn as needed. Use OneToMany on Author's books and ManyToOne on Book's author.