How do I join tables using TypeORM?

How do I join tables using TypeORM?

You can join tables in TypeORM using the QueryBuilder or by defining relations in your entity classes. Which method would you like to know more about?

Can you show me an example using QueryBuilder?

Sure! Here's a basic example:

const users = await getRepository(User)
  .createQueryBuilder('user')
  .leftJoinAndSelect('user.profile', 'profile')
  .getMany();

This will fetch users along with their profiles. Do you need more details?

What if I want to join multiple tables?

You can chain multiple joins like this:

const users = await getRepository(User)
  .createQueryBuilder('user')
  .leftJoinAndSelect('user.profile', 'profile')
  .leftJoinAndSelect('user.posts', 'posts')
  .getMany();

This will get users, their profiles, and their posts.

Thanks! Can you explain how to define relations in the entity?

Absolutely! In your entity class, you can define relations using decorators like @OneToMany, @ManyToOne, etc. For example:

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

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

This sets up a one-to-many relationship between User and Post.