MongoDB query to return specific fields from an array?

To return specific fields, use aggregate $project. Let us first create a collection with documents −

> db.returnSpecificFieldDemo.insertOne(    {       "StudentId":1,       "StudentDetails": [          {             "StudentName":"Larry",             "StudentAge":21,             "StudentCountryName":"US"          },          {             "StudentName":"Chris",             "StudentAge":23,             "StudentCountryName":"AUS"          }       ]    } ); {    "acknowledged" : true,    "insertedId" : ObjectId("5ce23d3236e8b255a5eee943") }

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

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

This will produce the following output −

{    "_id" : ObjectId("5ce23d3236e8b255a5eee943"),    "StudentId" : 1,    "StudentDetails" : [       {          "StudentName" : "Larry",          "StudentAge" : 21,          "StudentCountryName" : "US"       },       {          "StudentName" : "Chris",          "StudentAge" : 23,          "StudentCountryName" : "AUS"       }    ] }

Following is the query to return specific fields from an array −

> db.returnSpecificFieldDemo.aggregate([{$project:{_id:0, StudentId:'$StudentId', StudentCountryName:{ $arrayElemAt: ['$StudentDetails.StudentCountryName',1] }}}]);

This will produce the following output −

{ "StudentId" : 1, "StudentCountryName" : "AUS" }