查询它的最佳方法是什么？ 我喜欢写以下工作再上一个音符给予所有科目为：

  const subjectRepo = connection.getRepository(Subject);
  const response = await subjectRepo.find({
    relations: ['notes'],
    where: { note }
  });

但这会返回所有主题，而不仅仅是注释中的主题。

Reln定义为：

  @ManyToMany(() => Subject, (subject: Subject) => subject.notes)
  subjects: Subject[];

- 和 -

  @ManyToMany(() => Note, note => note.subjects)
  @JoinTable()
  notes: Note[];

执行的查询是：

SELECT "Subject"."id" AS "Subject_id", "Subject"."name" AS "Subject_name", "Subject"."description" AS "Subject_description", "Subject"."createdDate" AS "Subject_createdDate", "Subject"."updatedDate" AS "Subject_updatedDate", "Subject"."notebookId" AS "Subject_notebookId", "Subject"."measurementsId" AS "Subject_measurementsId", "Subject_notes"."id" AS "Subject_notes_id", "Subject_notes"."content" AS "Subject_notes_content", "Subject_notes"."notedAt" AS "Subject_notes_notedAt", "Subject_notes"."createdDate" AS "Subject_notes_createdDate", "Subject_notes"."updatedDate" AS "Subject_notes_updatedDate", "Subject_notes"."notebookId" AS "Subject_notes_notebookId" FROM "subject" "Subject" LEFT JOIN "subject_notes_note" "Subject_Subject_notes" ON "Subject_Subject_notes"."subjectId"="Subject"."id" LEFT JOIN "note" "Subject_notes" ON "Subject_notes"."id"="Subject_Subject_notes"."noteId"

注意：你可以这样做：

  return subjectRepo
    .createQueryBuilder('subject')
    .leftJoin('subject.notes', 'note')
    .where('note.id = :id', { id: note.id })
    .getMany();

但我希望采用较少的字符串和明确的连接方法

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提问于 2018-09-10

如何查询与TypeORM的多对多关系？

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用户回答回答于 2018-09-10

您试图让TypeORM生成的SQL大致如下

SELECT *
FROM subject
JOIN subject_note AS jt on jt.subject_id = subject.id
WHERE jt.note_id = :id

1.这是不可能的 repo.find

在编写本文时，无法where使用连接表创建子句repo.find(...)。您可以join（doc）但该where子句仅影响存储库的实体。

TypeORM也默默地忽略了无效的where子句，所以要小心。

2.重新选择备注实体

如果您想要所有subject给定的note，您将需要使用查询构建器，就像您所指出的那样，或者您需要使用它的关系重新选择注释对象。

note = await noteRepo.find({
    relations: ['subjects'],
    where: { id: note.id }
});
const subjects = note.subjects

3.使用TypeORM惰性关系

如果要避免重新选择，则需要使用TypeORM Lazy关系，但这会强制您将两个实体中的类型更改为Promise

// note entity
@ManyToMany(() => Subject, (subject: Subject) => subject.notes)
subjects: Promise<Subject[]>;

// subject entity
@ManyToMany(() => Note, note => note.subjects)
@JoinTable()
notes: Promise<Note[]>;

使用这种惰性关系，您需要await在每次使用之前加载链接的注释，但是您不需要为该find方法提供一系列关系。

const note = await noteRepo.find({
    where: { id: someId }
});
const subjects = await note.subjects