how to query parent document based on child reference document value?

[aniinprni]

Hi,
I am using mongoose. Here i have an requirement that i need to fetch student document when matches to its classRoomName name and rollNo. Here below is my student and classRoom schemas as follows:

1.student
===========
new Schema({

    rollNo:{type:Number, required:true},
    name:{type:String},
    classRoomRef:{type:Schema.Types.ObjectId,ref:'classRoom', required:true}
});

2.classRoom
============
new Schema({

    classRoomNo:{type:Number},
    classRoomName:{type:String}
});

I managed to get student document with rollNo . i have written the mongoose query like this below:

student.findOne({rollNo:"xxx"}),function(err,data){
  //printing data 
});

Now I need to retrieve student document based on classRoomName , i written below query but not working. Giving null.

student.findOne({rollNo:"xxx","classRoomRef.classRoomName":"yyy"}).populate("classRoomRef").exec(function(err,data){
  //printing data 
});

Kindly help me.

[aniinprni]

Hi,

Is there any update regarding this. Kindly let me know.

[vkarpov15]

Not possible to do that. .populate() is not a join, the above query simply finds students and then executes a separate query for the students' corresponding classRoomRef. If you want to query students by classRoomName, store classRoomName in the student doc.