MongoDB query to return only specific fields (phone numbers) in the form of an array?

To return only specific fields (phone numbers) as an array in MongoDB, use the distinct() method to extract unique values from nested fields across all documents in a collection.

Syntax

db.collection.distinct("field.path")

Sample Data

Let us create a collection with documents −

db.demo166.insertMany([
    {
        "details": {
            "UserName": "Chris",
            "UserAge": 29,
            "PhoneDetails": {
                "PhoneNumber": "98646463533"
            }
        }
    },
    {
        "details": {
            "UserName": "David", 
            "UserAge": 21,
            "PhoneDetails": {
                "PhoneNumber": "87664534654"
            }
        }
    }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e368b159e4f06af551997cf"),
        ObjectId("5e368b159e4f06af551997d0")
    ]
}

Verify Sample Data

Display all documents from the collection −

db.demo166.find();

{
    "_id": ObjectId("5e368b159e4f06af551997cf"),
    "details": {
        "UserName": "Chris",
        "UserAge": 29,
        "PhoneDetails": {
            "PhoneNumber": "98646463533"
        }
    }
}
{
    "_id": ObjectId("5e368b159e4f06af551997d0"),
    "details": {
        "UserName": "David",
        "UserAge": 21,
        "PhoneDetails": {
            "PhoneNumber": "87664534654"
        }
    }
}

Extract Phone Numbers as Array

Use distinct() to return only phone numbers in array format −

db.demo166.distinct("details.PhoneDetails.PhoneNumber");

["98646463533", "87664534654"]

How It Works

The distinct() method traverses all documents and extracts unique values from the specified nested field path "details.PhoneDetails.PhoneNumber", automatically returning them as an array format.

Conclusion

Use db.collection.distinct("field.path") to efficiently extract specific nested field values as an array. This method automatically handles duplicates and returns only unique values across all documents in the collection.