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 } ] }