Is that possible, to solve a complex mongoose populate query? - node.js

Question

I have four tables.
#First table
var mongoose=require('mongoose');
var Schema=mongoose.Schema;
#First table
var studentSchema=new Schema({
student_name: { type: String, required: true },
sendKey: { type: String },
created_by: { type:String },
updated_at: { type: Date, default: Date.now },
})
module.exports=mongoose.model('Student',studentSchema);
#Second table
var mongoose=require('mongoose');
var Schema=mongoose.Schema;
var institutionSchema=new Schema({
institution_name: { type: String, lowercase: true },
email: { type:String },
created_by: { type:String },
created_at: { type: Date, default: Date.now },
updated_at: { type: Date, default: Date.now },
})
module.exports=mongoose.model('Institution',institutionSchema);
#third table
var mongoose=require('mongoose');
// var Institution = ('./institution');
var Schema=mongoose.Schema;
var batchSchema=new Schema({
batch_name: { type: String, required: true },
institution: { type: Schema.Types.ObjectId, ref: 'Institution' },
created_by: { type:String },
created_at: { type: Date, default: Date.now },
updated_at: { type: Date, default: Date.now },
})
module.exports=mongoose.model('Batch',batchSchema);
#Fourth Table
var mongoose=require('mongoose');
var Schema=mongoose.Schema;
var batchtudentSchema=new Schema({
student_id: { type: Schema.Types.ObjectId, ref: 'Student', required : true},
batch_id: { type: Schema.Types.ObjectId, ref: 'Batch', required:true},
created_at: { type: Date, default: Date.now },
updated_at: { type: Date, default: Date.now },
})
module.exports=mongoose.model('BatchStudent',batchtudentSchema);
I have an institution Id. I want to find all students of this institution with Batch details.
Primarily I have tried to.. do that.
Student.find().populate('BatchStudent').pupulate('Batch').populate('Institution').exec((err, docs) => {
console.log(docs)
res.json(
{
data:docs
}
)
})
It is not working.. sending just all student data.. How can I get the data correctlly?

Answer 1

// Student Schema
var mongoose=require('mongoose');
var Schema=mongoose.Schema;
var studentSchema=new Schema({
student_name: {
type: String,
required: true
},
sendKey: {
type: String
},
batchStudent: {
type: Schema.Types.ObjectId,
ref: 'BatchStudent',
}
created_by: {
type:String
},
updated_at: {
type: Date,
default: Date.now
},
})
module.exports=mongoose.model('Student',studentSchema);
// BatchStudent Schema
var mongoose=require('mongoose');
var Schema=mongoose.Schema;
var batchtudentSchema=new Schema({
student_id: {
type: Schema.Types.ObjectId,
ref: 'Student',
required : true
},
batch_id: {
type: Schema.Types.ObjectId,
ref: 'Batch'
},
institution: {
type: Schema.Types.ObjectId,
ref: 'Institution'
}
})
module.exports=mongoose.model('BatchStudent',batchtudentSchema);
// Institution Schema
var mongoose=require('mongoose');
var Schema=mongoose.Schema;
var institutionSchema=new Schema({
institution_name: {
type: String,
lowercase: true
},
email: {
type: String
},
created_by: {
type:String
}
});
module.exports=mongoose.model('Institution',institutionSchema);
If the I removed created_at and updated_at to avoid duplication. Obey DRY principles always (Don't repeat yourself)
If you need to get the document you can simply use Deep Population/Association for that as shown below:
Student.find({}).populate({
path : 'batchStudent',
populate : {
path : 'institution'
}
}).exec(function (err, res) {
// do whatever you need to do here
})