TypeORM对将两个表映射到一起的表进行计数查询

// User 实体类
@Entity()
export class User {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @OneToMany(() => Post, post => post.user)
  posts: Post[];
}

// Post 实体类
@Entity()
export class Post {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  title: string;

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

import { getRepository } from 'typeorm';

// 获取 UserRepository 实例
const userRepository = getRepository(User);

// 查询指定用户的帖子数量
const userId = 1;
const postCount = await userRepository
  .createQueryBuilder('user')
  .leftJoinAndSelect('user.posts', 'post')
  .where('user.id = :userId', { userId })
  .getCount();

console.log(`User ${userId} has ${postCount} posts.`);