一对多查询

一对多关系描述

1. 一对多关系允许在 Entity1 可以拥有 Entity2 的多个实例时创建关系类型。
2. Entity2 只有一个 Entity1。Entity2 是关系的所有者，并在其自身存储 Entity1 主键列的值。
3. 两张表之间存在一对多关系，那么反之就是多对一的关系

相关注解说明

1. @OneToMany 注解

   // 源码内容
   export declare function OneToMany<T>(typeFunctionOrTarget: string | ((type?: any) => ObjectType<T>), inverseSide: string | ((object: T) => any), options?: RelationOptions): PropertyDecorator;
   改在
   

   接收三个参数：

   ​ typeFunctionOrTarget：关联查询的目标类型，即副表类，字符串类型或者一个返回目标类型的函数，必填

   ​ inverseSide: 副表实体类中关联主表的实体类属性，字符串类型或者一个返回目标类型的函数

   ​ options：用于配置关联关系

2. @ManyToOne 注解

   参数同上，主要说明如下：

   这里的 typeFunctionOrTarget 就是 One 所指的实体类，相应的就是主表类

   inverseSide 就是主表实体类上定义的副表(即当前表)的属性，也是函数

3. @JoinColumn 注解

   用于标注在一对一或者多对一的关系中配置关联关系，参数格式

   export interface JoinColumnOptions {
       // 主表中的主键列所对应的该表中的关联的列的列名称
       name?: string;
       // 引用此列的实体中的列的名称
       referencedColumnName?: string;
   }
   
   

User 实体类

import { Column, Entity, OneToMany, PrimaryColumn } from "typeorm";
import { Article } from "./article.entity";

@Entity('user')
export class User {
  @PrimaryColumn()
  id: string;

  @Column()
  nickname: string;

  @Column()
  username: string;

  @Column()
  password: string;

  @Column()
  avator: string;

  @Column()
  email: string;

  @OneToMany((type) => Article, (article) => article.user)
  articles: Article[];
}

备注：一对多的关系中，需要给主表的实体类设置一个副表关联的实体类属性，并通过 @OneToMany 进行注解，

Article 实体类

import { Column, Entity, JoinColumn, ManyToOne, PrimaryColumn } from "typeorm";
import { User } from "./user.entity";

@Entity('article')
export class Article {
  @PrimaryColumn()
  id: string;

  @Column()
  title: string;

  @Column()
  link: string;

  @Column()
  fileId: string;

  @Column('text')
  content: string;

  @Column()
  categoryId: string;

  @Column()
  formatId: number;

  @Column()
  originId: number;

  @Column()
  createBy: string;

  @ManyToOne((type) => User, (user) => user.articles)
  @JoinColumn({ name: 'createBy' })
  user: User;
}

链接关系

User.id === Article.createBy

服务

import { Injectable } from "@nestjs/common";
import { InjectRepository } from "@nestjs/typeorm";
import { Article } from "../../entities/article.entity";
import { Attachment } from "../../entities/attachment.entity";
import { Repository } from "typeorm";
import { User } from "../../entities/user.entity";

@Injectable()
export class UserService {
  constructor(@InjectRepository(User) private readonly userRepository: Repository<User>){}

  // 一对多查询
  getUserOfArticle () {
    return this.userRepository.find({
      relations: ['articles']
    })
  }
}

查询结果

[
    {
        "id": "16ffe4f0-98d0-11ea-adcb-cd4aa44d4464",
        "nickname": "李云龙",
        "username": "wanghailong",
        "password": "1bbd886460827015e5d605ed44252251",
        "avator": "http://192.168.1.101:8765/avator/f360e610-9d80-11ea-9008-019523360f5b.jpg",
        "email": "59652111558733@qq.com",
        "articles": [
            {
                "id": "0fcb8310-9c4a-11ea-9427-017d0539b705",
                "title": "fe'f",
                "link": null,
                "fileId": null,
                "content": "<p>微任务</p>",
                "categoryId": "4b958080-9a33-11ea-9abc-1d8c64f552b3",
                "formatId": 2,
                "originId": 1,
                "createBy": "16ffe4f0-98d0-11ea-adcb-cd4aa44d4464"
            },
             {
                "id": "11dbc240-9c46-11ea-9427-017d0539b705",
                "title": "antd design",
                "link": "https://www.antdv.com/components/form-cn/",
                "fileId": null,
                "content": null,
                "categoryId": "b8504210-99fb-11ea-ac42-a10a286651a2",
                "formatId": 3,
                "originId": 3,
                "createBy": "16ffe4f0-98d0-11ea-adcb-cd4aa44d4464"
            }
        ]
    }
]