Update object in array with a specific key in MongoDB

To update an object in an array with a specific key in MongoDB, use the $ positional operator with dot notation to match and update the desired array element based on a specific field value.

Syntax

db.collection.update(
    { "arrayName.keyField": "matchValue" },
    { $set: { "arrayName.$.updateField": "newValue" } }
);

Sample Data

Let us first create a collection with sample documents ?

db.demo419.insertOne({
    "ProductInformation": [
        {
            "ProductName": "Product-1",
            "ProductPrice": 500
        },
        {
            "ProductName": "Product-2",
            "ProductPrice": 600
        }
    ]
});

{
    "acknowledged": true,
    "insertedId": ObjectId("5e724762b912067e57771ae8")
}

Display all documents from the collection ?

db.demo419.find();

{
    "_id": ObjectId("5e724762b912067e57771ae8"),
    "ProductInformation": [
        { "ProductName": "Product-1", "ProductPrice": 500 },
        { "ProductName": "Product-2", "ProductPrice": 600 }
    ]
}

Example: Update Product Price by Product Name

Update the price of "Product-1" from 500 to 1250 ?

db.demo419.update(
    { "ProductInformation.ProductName": "Product-1" },
    { $set: { "ProductInformation.$.ProductPrice": 1250 } }
);

WriteResult({ "nMatched": 1, "nUpserted": 0, "nModified": 1 })

Verify Result

Display the updated document ?

db.demo419.find();

{
    "_id": ObjectId("5e724762b912067e57771ae8"),
    "ProductInformation": [
        { "ProductName": "Product-1", "ProductPrice": 1250 },
        { "ProductName": "Product-2", "ProductPrice": 600 }
    ]
}

Key Points

• The $ operator identifies the first array element matching the query condition.
• Use dot notation arrayName.$.fieldName to update specific fields within the matched object.
• Only the first matching array element gets updated if multiple elements match the criteria.

Conclusion

The $ positional operator combined with $set allows precise updates to objects within arrays by matching specific key values. This approach efficiently updates array elements without affecting other array items.