Querying only the field name and display only the id in MongoDB?

To query only the field name, set fieldName to 0 i.e. the fieldName to hide. Let us create a collection with documents −

> db.demo650.insertOne({_id:101,details:{Name:"Chris",Age:21}});
{ "acknowledged" : true, "insertedId" : 101 }
> db.demo650.insertOne({_id:102,details:{Name:"Bob",Age:22}});
{ "acknowledged" : true, "insertedId" : 102 }
> db.demo650.insertOne({_id:103,details:{Name:"Sam",Age:20}});
{ "acknowledged" : true, "insertedId" : 103 }
> db.demo650.insertOne({_id:104,details:{Name:"Robert",Age:24}});
{ "acknowledged" : true, "insertedId" : 104 }

Display all documents from a collection with the help of find() method −

> db.demo650.find();

This will produce the following output −

{ "_id" : 101, "details" : { "Name" : "Chris", "Age" : 21 } }
{ "_id" : 102, "details" : { "Name" : "Bob", "Age" : 22 } }
{ "_id" : 103, "details" : { "Name" : "Sam", "Age" : 20 } }
{ "_id" : 104, "details" : { "Name" : "Robert", "Age" : 24 } }

Following is how to query only the field name in MongoDB. We wanted to hide details field, therefore we have set it to 0 −

> db.demo650.find({},{details:0});

This will produce the following output −

{ "_id" : 101 }
{ "_id" : 102 }
{ "_id" : 103 }
{ "_id" : 104 }