How to search in array of object in MongoDB?

To search in an array of objects in MongoDB, use the $elemMatch operator. This operator matches documents where at least one array element satisfies multiple query conditions within the same object.

Syntax

db.collection.find({
    "arrayField": {
        $elemMatch: {
            "field1": "value1",
            "field2": "value2"
        }
    }
});

Sample Data

Let us create a collection with employee documents ?

db.searchArrayDemo.insertMany([
    {
        "EmployeeFirstName": "Adam",
        "EmployeeLastName": "Smith",
        "EmployeeDateOfBirth": new ISODate("1992-01-31T13:45:10Z"),
        "EmployeeSkills": ["Spring and Hibernate Framework", "Machine Learning"],
        "EmployeeDetails": [
            {
                "EmployeePerformanceArea": "Java",
                "Year": 2001
            },
            {
                "EmployeePerformanceArea": "Python",
                "Year": 2005
            }
        ]
    },
    {
        "EmployeeFirstName": "Carol",
        "EmployeeLastName": "Taylor",
        "EmployeeDateOfBirth": new ISODate("1993-04-21T11:10:20Z"),
        "EmployeeSkills": ["C++", "Cloud Computing"],
        "EmployeeDetails": [
            {
                "EmployeePerformanceArea": "C++",
                "Year": 1998
            },
            {
                "EmployeePerformanceArea": "C++ Game Developer",
                "Year": 2007
            }
        ]
    }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5c77b3812386c62d05142a6a"),
        ObjectId("5c77b58f2386c62d05142a6b")
    ]
}

Display all documents to verify the data ?

db.searchArrayDemo.find().pretty();

{
    "_id": ObjectId("5c77b3812386c62d05142a6a"),
    "EmployeeFirstName": "Adam",
    "EmployeeLastName": "Smith",
    "EmployeeDateOfBirth": ISODate("1992-01-31T13:45:10Z"),
    "EmployeeSkills": [
        "Spring and Hibernate Framework",
        "Machine Learning"
    ],
    "EmployeeDetails": [
        {
            "EmployeePerformanceArea": "Java",
            "Year": 2001
        },
        {
            "EmployeePerformanceArea": "Python",
            "Year": 2005
        }
    ]
}
{
    "_id": ObjectId("5c77b58f2386c62d05142a6b"),
    "EmployeeFirstName": "Carol",
    "EmployeeLastName": "Taylor",
    "EmployeeDateOfBirth": ISODate("1993-04-21T11:10:20Z"),
    "EmployeeSkills": [
        "C++",
        "Cloud Computing"
    ],
    "EmployeeDetails": [
        {
            "EmployeePerformanceArea": "C++",
            "Year": 1998
        },
        {
            "EmployeePerformanceArea": "C++ Game Developer",
            "Year": 2007
        }
    ]
}

Case 1: When Element is Found

Search for employees with C++ performance area in year 1998 ?

db.searchArrayDemo.find({
    "EmployeeDetails": {
        $elemMatch: {
            "EmployeePerformanceArea": "C++",
            "Year": 1998
        }
    }
}).pretty();

{
    "_id": ObjectId("5c77b58f2386c62d05142a6b"),
    "EmployeeFirstName": "Carol",
    "EmployeeLastName": "Taylor",
    "EmployeeDateOfBirth": ISODate("1993-04-21T11:10:20Z"),
    "EmployeeSkills": [
        "C++",
        "Cloud Computing"
    ],
    "EmployeeDetails": [
        {
            "EmployeePerformanceArea": "C++",
            "Year": 1998
        },
        {
            "EmployeePerformanceArea": "C++ Game Developer",
            "Year": 2007
        }
    ]
}

Case 2: When Element is Not Found

Search for non−existent combination of C performance area in year 1996 ?

db.searchArrayDemo.find({
    "EmployeeDetails": {
        $elemMatch: {
            "EmployeePerformanceArea": "C",
            "Year": 1996
        }
    }
}).pretty();

(No documents returned)

Key Points

• $elemMatch ensures all conditions are matched within a single array element.
• Without $elemMatch, conditions might match different array elements.
• Returns the entire document if any array element matches all conditions.

Conclusion

Use $elemMatch to search array of objects when you need multiple conditions to match within the same array element. This ensures precise matching and prevents cross−element condition matching.