如何从Typeorm中的联接实体中仅选择单个/多个字段

Question

根据TypeOrm文档：https://github.com/typeorm/typeorm/blob/master/docs/select-query-builder.md#joining-relations

我们可以查询连接的实体的字段，该字段将填充所有的字段到响应中。我不确定如何限制只有几个选定的字段(单个/多个)，我尝试添加'select([])‘，但它在生成的SQL查询中不起作用，我可以看到它正在查询所有字段。

代码：

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;
}

在代码中：

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

上面的代码给出的输出是-

{
    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"
    }]
}

有没有办法我只能查询'url‘和'alt’，这样输出就会像这样--

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

Answer 1

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

或

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

(对第二个不太确定)

Answer 2

Art Olshansky给出的第一个答案是正确的(第二个答案不是)，所以，你必须站在“基本”实体上，但是，如果你不需要所有/任何用户字段，你可以直接应用

​

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

​