How to get a specific object from array of objects inside specific MongoDB document?

To get a specific object from array of objects inside a MongoDB document, use the positional operator $ in the projection to return only the matched array element.

Syntax

db.collection.find(
    { "arrayField.subField": "matchValue" },
    { "_id": 0, "arrayField.$": 1 }
);

Sample Data

Let us create a collection with documents −

db.getASpecificObjectDemo.insertOne({
    _id: 1,
    "CustomerName": "Larry",
    "CustomerDetails": {
        "CustomerPurchaseDescription": [
            {
                "id": 100,
                "ProductName": "Product-1",
                "Amount": 10000
            },
            {
                "id": 101,
                "ProductName": "Product-2",
                "Amount": 10500
            },
            {
                "id": 102,
                "ProductName": "Product-3",
                "Amount": 10200
            }
        ]
    }
});

{ "acknowledged": true, "insertedId": 1 }

Display all documents from the collection −

db.getASpecificObjectDemo.find().pretty();

{
    "_id": 1,
    "CustomerName": "Larry",
    "CustomerDetails": {
        "CustomerPurchaseDescription": [
            {
                "id": 100,
                "ProductName": "Product-1",
                "Amount": 10000
            },
            {
                "id": 101,
                "ProductName": "Product-2",
                "Amount": 10500
            },
            {
                "id": 102,
                "ProductName": "Product-3",
                "Amount": 10200
            }
        ]
    }
}

Example

Get the specific object with id 101 from the array −

db.getASpecificObjectDemo.find(
    { _id: 1, "CustomerDetails.CustomerPurchaseDescription.id": 101 },
    { _id: 0, "CustomerDetails.CustomerPurchaseDescription.$": 1 }
);

{
    "CustomerDetails": {
        "CustomerPurchaseDescription": [
            {
                "id": 101,
                "ProductName": "Product-2",
                "Amount": 10500
            }
        ]
    }
}

Key Points

• The $ operator returns only the first matching element from the array.
• Use dot notation to match nested array fields in the query condition.
• The projection field must match the same path as used in the query condition.

Conclusion

The positional operator $ efficiently retrieves specific objects from arrays by matching query conditions and projecting only the matched element. This approach is ideal when you need a single matching object rather than the entire array.