How Do I Build This Inner Join Query With TypeORM's QueryBuilder?

Question

I'm trying to learn TypeORM, I haven't really used an ORM before. I'm having trouble understanding the documentation and other examples online.

I just want to use the TypeORM QueryBuilder to generate the following query.

select first_name, last_name
from users u
inner join company_relations cr
on u.id = cr.id

Thank you for any help!

Answer 1

You need to work 2 elements, your entities and the query.

For example, your entities should look more or less like this

UserEntity.ts

@Entity('users')
export class UsersEntity {

    // other attributes

    @Column({ name: 'first_name', type: 'varchar' })
    firstName: string;

    @Column({ name: 'last_name', type: 'varchar' })
    lastName: string;

    @OneToMany(
      () => CompanyRelationsEntity,
      (companyRelationsEntity: CompanyRelationsEntity) => companyRelationsEntity.userId,
    )
    companyRelations: CompanyRelationEntity[];
}

CompanyRelationEntity.ts

@Entity('company_relations')
export class CompanyRelationEntity {

    // Other attributes

    @ManyToOne(
      () => UsersEntity,
      (userEntity: UsersEntity) => usersEntity.companyRelations,
    )
    @JoinColumn({ name: 'user_id', referencedColumnName: 'id' })
    user: UserEntity;
}

Then, you can perform a query similar to this

await this.repository
    .createQueryBuilder('u')
    .select(['u.firstName', 'u.lastName'])
    .innerJoin('m.companyRelations', 'cr')
    .getOne();

You can read more about this in its official link