Query array of nested string with MongoDB?

To query array of nested string in MongoDB, you can use dot notation to access nested array elements. This allows you to search for specific string values within arrays that are nested inside other objects.

Syntax

db.collection.find({"parentField.nestedArrayField": "searchValue"})

Sample Data

Let us first create a collection with documents containing nested arrays of strings ?

db.nestedStringDemo.insertMany([
    {
        "CustomerName": "John",
        "CustomerOtherDetails": [
            { "Age": 29, "CountryName": "US" },
            {
                "CompanyName": "Amazon",
                "Salary": 150000,
                "ProjectName": ["Online Library Management System", "Pig Dice Game"]
            }
        ]
    },
    {
        "CustomerName": "Chris",
        "CustomerOtherDetails": [
            { "Age": 27, "CountryName": "AUS" },
            {
                "CompanyName": "Google",
                "Salary": 250000,
                "ProjectName": ["Chat Application", "Game Design"]
            }
        ]
    }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5cea4629ef71edecf6a1f690"),
        ObjectId("5cea466eef71edecf6a1f691")
    ]
}

Display All Documents

db.nestedStringDemo.find().pretty();

{
    "_id": ObjectId("5cea4629ef71edecf6a1f690"),
    "CustomerName": "John",
    "CustomerOtherDetails": [
        {
            "Age": 29,
            "CountryName": "US"
        },
        {
            "CompanyName": "Amazon",
            "Salary": 150000,
            "ProjectName": [
                "Online Library Management System",
                "Pig Dice Game"
            ]
        }
    ]
}
{
    "_id": ObjectId("5cea466eef71edecf6a1f691"),
    "CustomerName": "Chris",
    "CustomerOtherDetails": [
        {
            "Age": 27,
            "CountryName": "AUS"
        },
        {
            "CompanyName": "Google",
            "Salary": 250000,
            "ProjectName": [
                "Chat Application",
                "Game Design"
            ]
        }
    ]
}

Query Array of Nested Strings

Now, let us query an array of nested string using dot notation to find documents where ProjectName contains "Chat Application" ?

db.nestedStringDemo.find({"CustomerOtherDetails.ProjectName": "Chat Application"}).pretty();

{
    "_id": ObjectId("5cea466eef71edecf6a1f691"),
    "CustomerName": "Chris",
    "CustomerOtherDetails": [
        {
            "Age": 27,
            "CountryName": "AUS"
        },
        {
            "CompanyName": "Google",
            "Salary": 250000,
            "ProjectName": [
                "Chat Application",
                "Game Design"
            ]
        }
    ]
}

Conclusion

Use dot notation with the format parentField.nestedArrayField to query nested string arrays in MongoDB. This automatically searches through array elements to find matching values within the nested structure.