TypeORM级联选项:级联，onDelete，onUpdate [英] TypeORM cascade option: cascade, onDelete, onUpdate

问题描述

TypeORM中的级联选项是否重叠或它们的用途完全不同?文档中对它们的描述非常稀缺，部分缺失，或者我找不到.

Do cascade options in TypeORM overlap or do they have a completely different purpose? Their description in the documentation is very scarce and partly missing, or I couldn't find it.

IOW，请执行以下选项

IOW, do the following options

{级联:"update"} = {onUpdate:'CASCADE'}

{级联:删除"} = {onDelete:'CASCADE'}

有同样的效果吗?

还是 cascade 选项仅用于TypeORM，而 onUpdate 和 onDelete 仅用于DB模式(通过迁移创建)?

Or the cascade option is only for the TypeORM use while onUpdate and onDelete are only for the DB schema (created by migration)?

推荐答案

这是我研究它的结论:

cascade 选项不会影响数据库列约束，我相信TypeORM仅将其用于评估如何将实体关系保存到数据库中.我们可以这样定义实体:

The cascade option does not affect the database column constraints, and I believe is used by TypeORM only in evaluating how to save entity relations to the database. We can define entities like this:

@Entity()
class Book extends BaseEntity {
    @ManyToOne(() => Author, (author) => author.books, {
        onDelete: 'CASCADE',
    })
    public author?: Author
}

@Entity()
class Author extends BaseEntity {
    @OneToMany(() => Book, (book) => book.author, {
        cascade: true,
    })
    public books: Book[];
}

onDelete 将 authorId 外键设置为 Book 上的CASCADE onDelete.这意味着当作者被删除时，这本书也将被删除.

onDelete sets the authorId foreign key to CASCADE onDelete on Book. This means that when the author is deleted, the book is also deleted.

在 Author 上设置 cascade:true 会告诉TypeORM:如果在作者身上添加了新书并且保存了作者，则还应将新书保存到数据库.像这样:

Setting cascade: true on Author tells TypeORM that if a new book is appended on an author and the author is saved, the new book should also be saved to the database. Like this:

const author = await Author.findOne({ id: '123' });
author.books.push(new Book(...));
await author.save();

如果未在 Book 上设置级联，则新书不会保存到数据库中.

If cascade is not set on Book, the new book will not be saved to the database.

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