创建多对一/一对多关系

创建多对一/一对多关系

让我们创建一个多对一/一对多的关系。假设一个 photo 有一个 author，每个 author 都可以有多个 photos。首先让我们创建一个Author类：

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

@Entity()
export class Author {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @OneToMany(type => Photo, photo => photo.author) // note: we will create author property in the Photo class below
  photos: Photo[];
}

Author 包含反向关系。OneToMany 总是反向的, 并且总是与 ManyToOne一起出现。

现在让我们将关系的所有者方添加到 Photo 实体中：

import { Entity, Column, PrimaryGeneratedColumn, ManyToOne } from "typeorm";
import { PhotoMetadata } from "./PhotoMetadata";
import { Author } from "./Author";

@Entity()
export class Photo {
  /* ... other columns */

  @ManyToOne(type => Author, author => author.photos)
  author: Author;
}

在多对一/一对多的关系中，拥有方总是多对一的。这意味着使用@ManyToOne的类将存储相关对象的 id。运行应用程序后，ORM 将创建author表：

+-------------+--------------+----------------------------+
|                          author                         |
+-------------+--------------+----------------------------+
| id          | int(11)      | PRIMARY KEY AUTO_INCREMENT |
| name        | varchar(255) |                            |
+-------------+--------------+----------------------------+

它还将修改photo表，添加新的author列并为其创建外键：

+-------------+--------------+----------------------------+
|                         photo                           |
+-------------+--------------+----------------------------+
| id          | int(11)      | PRIMARY KEY AUTO_INCREMENT |
| name        | varchar(255) |                            |
| description | varchar(255) |                            |
| filename    | varchar(255) |                            |
| isPublished | boolean      |                            |
| authorId    | int(11)      | FOREIGN KEY                |
+-------------+--------------+----------------------------+