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

To query only specific fields in MongoDB, use projection to control which fields appear in the result. Set field values to 1 to include or 0 to exclude them from the output.

Syntax

db.collection.find(query, projection);

// Include specific fields
db.collection.find({}, {fieldName: 1});

// Exclude specific fields  
db.collection.find({}, {fieldName: 0});

Sample Data

db.demo650.insertMany([
    {_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}}
]);

{
    "acknowledged": true,
    "insertedIds": {
        "0": 101,
        "1": 102,
        "2": 103,
        "3": 104
    }
}

Display All Documents

db.demo650.find();

{ "_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 } }

Example: Hide Details Field, Show Only _id

To exclude the details field and display only the _id, set details to 0 ?

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

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

Key Points

• The _id field is included by default unless explicitly excluded with _id: 0.
• Use 0 to exclude fields and 1 to include specific fields.
• You cannot mix inclusion and exclusion projections (except for _id).

Conclusion

MongoDB projection allows you to control query output by including or excluding specific fields. Use 0 to hide unwanted fields while keeping the _id field visible by default.