Finding highest value from sub-arrays in MongoDB documents?

To find the highest value from sub-arrays in MongoDB documents, use the aggregation framework with $unwind, $sort, and $limit operators to flatten arrays, sort by the target field, and return the top result.

Syntax

db.collection.aggregate([
    { $unwind: "$arrayField" },
    { $sort: { "arrayField.valueField": -1 } },
    { $limit: 1 }
]);

Sample Data

db.findHighestValueDemo.insertMany([
    {
        _id: 10001,
        "StudentDetails": [
            { "StudentName": "Chris", "StudentMathScore": 56},
            { "StudentName": "Robert", "StudentMathScore": 47 },
            { "StudentName": "John", "StudentMathScore": 98 }
        ]
    },
    {
        _id: 10002,
        "StudentDetails": [
            { "StudentName": "Ramit", "StudentMathScore": 89},
            { "StudentName": "David", "StudentMathScore": 76 },
            { "StudentName": "Bob", "StudentMathScore": 97 }
        ]
    }
]);

{ "acknowledged" : true, "insertedIds" : [ 10001, 10002 ] }

Example: Find Highest Math Score

Find the student with the highest math score across all documents ?

db.findHighestValueDemo.aggregate([
    { $project: {"StudentDetails.StudentName": 1, "StudentDetails.StudentMathScore": 1} },
    { $unwind: "$StudentDetails" },
    { $sort: {"StudentDetails.StudentMathScore": -1} },
    { $limit: 1 }
]);

{
    "_id" : 10001,
    "StudentDetails" : {
        "StudentName" : "John",
        "StudentMathScore" : 98
    }
}

How It Works

• $project ? Selects only the required fields from StudentDetails array
• $unwind ? Flattens the StudentDetails array, creating separate documents for each student
• $sort ? Orders documents by StudentMathScore in descending order (-1)
• $limit ? Returns only the first (highest scoring) document

Conclusion

Use aggregation pipeline with $unwind to flatten arrays, $sort to order by value, and $limit to get the highest value. This approach works efficiently across multiple documents and sub-arrays.