How to select only single/multiple fields from joined entity in Typeorm

Question

accord to TypeOrm doc: https://github.com/typeorm/typeorm/blob/master/docs/select-query-builder.md#joining-relations

We can query the joined entity's field that will populate all its field into the response. I am not sure how to restrict only to few selected fields(single/multiple), I tried adding 'select([])' but it is not working in the generated SQL query I can see it is querying all the fields.

code:

import {Entity, PrimaryGeneratedColumn, Column, OneToMany} from "typeorm";
import {Photo} from "./Photo";

@Entity()
export class User {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    name: string;

    @OneToMany(type => Photo, photo => photo.user)
    photos: Photo[];
}
import {Entity, PrimaryGeneratedColumn, Column, ManyToOne} from "typeorm";
import {User} from "./User";

@Entity()
export class Photo {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    url: string;

    @Column()
    alt: string;

    @ManyToOne(type => User, user => user.photos)
    user: User;
}

and on the code:

const user = await createQueryBuilder("user")
    .leftJoinAndSelect("user.photos", "photo")
    .where("user.name = :name", { name: "Timber" })
    .getOne();

The above code gives the output as -

{
    id: 1,
    name: "Timber",
    photos: [{
        id: 1,
        url: "me-with-chakram.jpg",
        alt: "Me With Chakram"
    }, {
        id: 2,
        url: "me-with-trees.jpg",
        alt: "Me With Trees"
    }]
}

Is there a way I can query only 'url' and 'alt' so the output will look something like this -

{
    id: 1,
    name: "Timber",
    photos: [{
        url: "me-with-chakram.jpg",
        alt: "Me With Chakram"
    }, {
        url: "me-with-trees.jpg",
        alt: "Me With Trees"
    }]
}

Solution

const user = await createQueryBuilder("user")
    .leftJoinAndSelect("user.photos", "photo")
    .select(['user', 'photo.url', 'photo.alt'])
    .where("user.name = :name", { name: "Timber" })
    .getOne();

or

const user = await createQueryBuilder("user")
    .leftJoinAndSelect("user.photos", "photo")
    .addSelect(['photo.url', 'photo.alt'])
    .where("user.name = :name", { name: "Timber" })
    .getOne();

(not sure about the second one)

Comments

[Dev AKS]

Thanks for your answer. I figured eventually but you were quick with your response :)

[Dev AKS]

The first one is correct, the second is idle for function use (SUM, AVG, etc).

[Samuel Goldenbaum]

This returns ALL photo fields

[D.Zotov]

How your answer is different from the accepted one?

[Jhon Zambrano]

My answer is just a complement, and refers to the fact you can not remove at all the user entity (who owns relationship) from select statement regardless you don't need any field from user just photo, you must select at least one field from user entity

[Dipak]

Is the output of query same as requested question?