TypeORM - Relations

20220930-備註更新此篇文章為 0.2.x

關聯式資料庫相關關聯狀態

one-to-one using @OneToOne
many-to-one using @ManyToOne
one-to-many using @OneToMany
many-to-many using @ManyToMany

@JoinColumn()

有 @JoinColumn() 的那方Table 才會有多 Column 可以忽略使用於 @ManyToOne / @OneToMany

@JoinTable()

@ManyToMany 情境下會有多一張表去關聯

One-to-one

/entities/Profile.ts

import {Entity, PrimaryGeneratedColumn, Column} from "typeorm";

@Entity()
export class Profile {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    gender: string;

    @Column()
    photo: string;

    @OneToOne(() => User, user => user.profile)
    user: User;

}

/entities/User.ts

import {Entity, PrimaryGeneratedColumn, Column, OneToOne, JoinColumn} from "typeorm";
import {Profile} from "./Profile";

@Entity()
export class User {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    name: string;

    @OneToOne(() => Profile, profile => profile.user)
    @JoinColumn()
    profile: Profile;

}

MySQL Tables

+-------------+--------------+----------------------------+
|                        profile                          |
+-------------+--------------+----------------------------+
| id          | int(11)      | PRIMARY KEY AUTO_INCREMENT |
| gender      | varchar(255) |                            |
| photo       | varchar(255) |                            |
+-------------+--------------+----------------------------+

+-------------+--------------+----------------------------+
|                          user                           |
+-------------+--------------+----------------------------+
| id          | int(11)      | PRIMARY KEY AUTO_INCREMENT |
| name        | varchar(255) |                            |
| profileId   | int(11)      | FOREIGN KEY                |
+-------------+--------------+----------------------------+

Many-to-one / One-to-Many

可忽略 @JoinColumn()
使用 @OneToMany，@ManyToOne則為必填
使用 @ManyToOne，@OneToMany則非必填

/entities/User.ts

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

@Entity()
export class User {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    name: string;

    @OneToMany(() => Photo, photo => photo.user)
    photos: Photo[];

}

/entities/Photo.ts

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

@Entity()
export class Photo {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    url: string;

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

    // 這可以不用加，如果要幫欄位加上註解，可以加，ManyToOne會自動加這個 Colum 不用另外加上 @JoinColum()
    // @Column({ comment: 'userId'})
    // userId: string;
}

MySQL Table

+-------------+--------------+----------------------------+
|                         photo                           |
+-------------+--------------+----------------------------+
| id          | int(11)      | PRIMARY KEY AUTO_INCREMENT |
| url         | varchar(255) |                            |
| userId      | int(11)      | FOREIGN KEY                |
+-------------+--------------+----------------------------+

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

many-to-many

/entities/Category.ts

import {Entity, PrimaryGeneratedColumn, Column} from "typeorm";

@Entity()
export class Category {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    name: string;

}

/entities/Question.ts

import {Entity, PrimaryGeneratedColumn, Column, ManyToMany, JoinTable} from "typeorm";
import {Category} from "./Category";

@Entity()
export class Question {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    title: string;

    @Column()
    text: string;

    @ManyToMany(() => Category)
    @JoinTable({ name: 'question_category' })
    categories: Category[];
}

MySQL Table

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

+-------------+--------------+----------------------------+
|                        question                         |
+-------------+--------------+----------------------------+
| id          | int(11)      | PRIMARY KEY AUTO_INCREMENT |
| title       | varchar(255) |                            |
| text        | varchar(255) |                            |
+-------------+--------------+----------------------------+

+-------------+--------------+----------------------------+
|                    question_category                    |
+-------------+--------------+----------------------------+
| questionId  | int(11)      | PRIMARY KEY FOREIGN KEY    |
| categoryId  | int(11)      | PRIMARY KEY FOREIGN KEY    |
+-------------+--------------+----------------------------+