如何在猫鼬中执行内部联接

Question

我过去两天一直在Google搜索，但没有成功。我需要用两种模式在猫鼬中执行内部联接，但没有得到其他集合的响应。我的问题是我的代码中缺少什么？请帮助我。

我也想获得课程和科目的成绩。

  exports.classSubjectList = async (req, res, next) => {
  const obj = await ClassSubject.find().populate('classmodel').exec();
  res.status(200).json({
        success: true,
        response: obj
      });
};

// ClassSubjectModel

const mongoose = require('mongoose');
mongoose.Promise = global.Promise 
const Schema = mongoose.Schema
const classModel  = require('../class/classModel');
const subjectModel  = require('../subject/subjectModel');

var classsubject = new Schema({    
    ClassId: String,
    SubjectId : String,
    IsShow: { type: Boolean, default : true},   
    classmodel: { type: mongoose.Schema.Types.ObjectId, ref: classModel },
    subjectmodel: { type: mongoose.Schema.Types.ObjectId, ref: subjectModel },

});

// Class Model

const mongoose = require('mongoose');
mongoose.Promise = global.Promise 
const Schema = mongoose.Schema

var classinfo = new Schema({    
    ClassName: String,
    IsShow: { type: Boolean, default : true},   

});


module.exports = mongoose.model('classinfo', classinfo);

//主题模型

const mongoose = require('mongoose');
mongoose.Promise = global.Promise 
const Schema = mongoose.Schema

var subject = new Schema({    
    SubjectName: String,
    IsShow: Boolean,   

});


module.exports = mongoose.model('subject', subject);

结果

[
        {
            "IsShow": true,
            "_id": "5e1efc0f354849246c472cfe",
            "SubjectId": "5e1da60bf52acb30b87e92c4",
            "ClassId": "5e1ec13ed777bf28d01e2481",          
            "__v": 0
        }]

Answer 1

您应将ref定义为架构的名称，而不是对象的引用

这样做吧

classmodel: { type: mongoose.Schema.Types.ObjectId, ref: 'classinfo' } 
subjectmodel: { type: mongoose.Schema.Types.ObjectId, ref: 'subject' },
// here 'classinfo' & 'subject' are the names you defined your schema with 

如果要适当的内部联接，则应同时填充这两者

const obj = await ClassSubject.find().populate('classmodel').populate('subject').exec();

希望这会有所帮助