How to retrieve a nested object in MongoDB?

To retrieve a nested object in MongoDB, use $ operator. Let us first create a collection with documents −

> db.queryNestedObject.insertOne(
...    {
...       "StudentName" : "James",
...       "StudentSubjectScore" : [
...          {"StudentMongoDBScore":98},
...          {"StudentCScore":92},
...          {"StudentJavaScore":91}
...       ]
...    }
... );
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ccf49a9dceb9a92e6aa1962")
}

Following is the query to display all documents from a collection with the help of find() method −

> db.queryNestedObject.find().pretty();

This will produce the following output −

{
   "_id" : ObjectId("5ccf49a9dceb9a92e6aa1962"),
   "StudentName" : "James",
   "StudentSubjectScore" : [
      {
         "StudentMongoDBScore" : 98
      },
      {
         "StudentCScore" : 92
      },
      {
         "StudentJavaScore" : 91
      }
   ]
}

Following is the query to retrieve a nested object −

> db.queryNestedObject.find({'StudentSubjectScore.StudentJavaScore' : 91},{'StudentSubjectScore.$': 1 , _id: 0});

This will produce the following output −

{ "StudentSubjectScore" : [ { "StudentJavaScore" : 91 } ] }