Selecting only a single field from MongoDB?

To select only a single field from MongoDB, use the projection parameter in the find() method. Set the desired field to 1 to include it, and set _id to 0 to exclude the default ID field.

Syntax

db.collection.find(
    { query },
    { fieldName: 1, _id: 0 }
);

Sample Data

db.selectingASingleFieldDemo.insertMany([
    {"StudentFirstName": "John", "StudentAge": 23, "StudentCountryName": "US"},
    {"StudentFirstName": "Carol", "StudentAge": 21, "StudentCountryName": "UK"},
    {"StudentFirstName": "David", "StudentAge": 24, "StudentCountryName": "AUS"},
    {"StudentFirstName": "Robert", "StudentAge": 26, "StudentCountryName": "AUS"}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5cd547142cba06f46efe9f02"),
        ObjectId("5cd5471f2cba06f46efe9f03"),
        ObjectId("5cd5472c2cba06f46efe9f04"),
        ObjectId("5cd548382cba06f46efe9f05")
    ]
}

Example 1: Select Single Field Without Conditions

Select only the StudentFirstName field from all documents ?

db.selectingASingleFieldDemo.find(
    {},
    { StudentFirstName: 1, _id: 0 }
);

{ "StudentFirstName": "John" }
{ "StudentFirstName": "Carol" }
{ "StudentFirstName": "David" }
{ "StudentFirstName": "Robert" }

Example 2: Select Single Field with Query Conditions

Select only StudentFirstName for students older than 21 from Australia ?

db.selectingASingleFieldDemo.find(
    { 
        $and: [
            { StudentAge: { $gt: 21 } },
            { "StudentCountryName": "AUS" }
        ] 
    },
    { StudentFirstName: 1, _id: 0 }
);

{ "StudentFirstName": "David" }
{ "StudentFirstName": "Robert" }

Key Points

• Set field to 1 to include it in results.
• Set _id: 0 to exclude the default ID field.
• Combine projection with query conditions for filtered single-field results.

Conclusion

Use projection in MongoDB's find() method to select only specific fields. Set desired fields to 1 and _id to 0 for clean single-field output.