How to return only some columns of a relations with Typeorm

Question

Ok, I'm having trouble with getting the relations with typeorm. When I run the service it returns all the data from the relation, and I want only specific fields, like id and name.

Here's my code:

async findById(id: string): Promise<UsersUseOfferHistoric> {
return await this.repository.findOne({
  where: { id },
  relations: ['userId', 'offerId'],
  });
}

Here's the JSON output:

{
"id": "da0fd04e-17c6-4412-b342-a4361d191468",
"createdAt": "2020-01-07T19:48:30.840Z",
"userId": {
    "id": "bdc00227-569f-44b5-9bdd-c8de03661ebd",
    "name": "Alexandre Vieira",
    "cpf": "10443771430",
    "email": "av.souza2018@gmail.com",
    "password": "asjdsifjdsfasf",
    "imagePath": "/me.png",
    "active": true,
    "lastLogin": "2020-01-07T19:40:26.850Z",
    "createdAt": "2020-01-07T19:40:26.850Z",
    "updatedAt": "2020-01-07T19:40:26.850Z"
},
"offerId": {
    "id": "e399560c-d2c2-4f4e-b2b1-94cae3af3779",
    "offerDrescription": "Nova oferta top",
    "discountCoupon": " Desconto top",
    "discountValidity": "2020-01-07T14:18:19.803Z",
    "discountPercentage": 20,
    "discountQuantityLimit": 50,
    "createdAt": "2020-01-07T19:45:33.589Z",
    "updatedAt": "2020-01-07T19:45:33.589Z"
   }
}

Here's the output I want:

{
"id": "da0fd04e-17c6-4412-b342-a4361d191468",
"createdAt": "2020-01-07T19:48:30.840Z",
"userId": {
    "id": "bdc00227-569f-44b5-9bdd-c8de03661ebd",
    "name": "Alexandre Vieira",
   
},
"offerId": {
    "id": "e399560c-d2c2-4f4e-b2b1-94cae3af3779",
    "offerDrescription": "Nova oferta top",
   
   }
}

Answer 1

The findOne function accepts an select: ['id', 'createdAt'] property where you can filter the fields of the outgoing relation. To explicitly select the returned fields of a joined table (using the relations property does implicitly a left join) you have to use a query builder.

await getRepository(Foo).createQueryBuilder('foo')
  .where({ id: 1})
  .select(['foo.id', 'foo.createdAt', 'bar.id', 'bar.name'])
  .leftJoin('foo.bars', 'bar')  // bar is the joined table
  .getMany();