MongoDB query to return specific fields from an array?

MongoDB Online Training

44 Lectures 3 hours

Arnab Chakraborty

More Detail

MongoDB For Absolute Beginners

54 Lectures 5.5 hours

Eduonix Learning Solutions

More Detail

ASP.NET Core 3 MVC Application with MongoDB

44 Lectures 4.5 hours

Kaushik Roy Chowdhury

More Detail

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" }

Smita Kapse

Updated on 30-Jul-2019 22:30:26

• Related Questions & Answers
• MongoDB query to return only specific fields (phone numbers) in the form of an array?
• MongoDB query to sum specific fields
• MongoDB query to get only specific fields in nested array documents?
• How to query a document in MongoDB comparing fields from an array?
• How to project specific fields from a document inside an array in Mongodb?
• MongoDB query to get record beginning with specific element from an array?
• Query an array in MongoDB to fetch a specific value
• MongoDB query to update selected fields
• MongoDB query to concatenate values of array with other fields
• Is it possible to return a list of specific values from a MongoDB query?
• MongoDB query to find data from an array inside an object?
• Sort array in MongoDB query and project all fields?
• Update only specific fields in MongoDB?
• MongoDB query to match and remove element from an array?
• MongoDB inverse of query to return all items except specific documents?