MongoDB query for a single field

To query a single field in MongoDB, use the find() method with projection. Projection allows you to specify which fields to include or exclude from the query results.

Syntax

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

Sample Data

Let us first create a collection with documents ?

db.demo10.insertMany([
    { "StudentId": 101, "StudentName": "Chris" },
    { "StudentId": 102, "StudentName": "David" },
    { "StudentId": 103, "StudentName": "Bob" }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e0f68a7d7df943a7cec4f9b"),
        ObjectId("5e0f68afd7df943a7cec4f9c"),
        ObjectId("5e0f68b5d7df943a7cec4f9d")
    ]
}

Display All Documents

Following is the query to display all documents from a collection ?

db.demo10.find();

{ "_id": ObjectId("5e0f68a7d7df943a7cec4f9b"), "StudentId": 101, "StudentName": "Chris" }
{ "_id": ObjectId("5e0f68afd7df943a7cec4f9c"), "StudentId": 102, "StudentName": "David" }
{ "_id": ObjectId("5e0f68b5d7df943a7cec4f9d"), "StudentId": 103, "StudentName": "Bob" }

Query Single Field

Here is the query to retrieve only the StudentName field ?

db.demo10.find({}, { "_id": 0, "StudentId": 0 });

{ "StudentName": "Chris" }
{ "StudentName": "David" }
{ "StudentName": "Bob" }

Alternative Method

You can also explicitly include only the required field ?

db.demo10.find({}, { "StudentName": 1, "_id": 0 });

{ "StudentName": "Chris" }
{ "StudentName": "David" }
{ "StudentName": "Bob" }

Conclusion

Use projection with find() to query specific fields. Set unwanted fields to 0 to exclude them, or set desired fields to 1 to include only those fields in the result.