Find maximum score for duplicate Name values in MongoDB?

To find the maximum score for duplicate Name values in MongoDB, use the aggregation pipeline with $group and $max operators. This groups documents by name and calculates the highest score for each group.

Syntax

db.collection.aggregate([
    {
        $group: {
            _id: "$fieldName",
            maxScore: { $max: "$scoreField" }
        }
    }
]);

Sample Data

db.demo114.insertMany([
    { "Score": 60, "Name": "Chris" },
    { "Score": 87, "Name": "Chris" },
    { "Score": 45, "Name": "David" },
    { "Score": 67, "Name": "Chris" },
    { "Score": 38, "Name": "David" }
]);

{
    "acknowledged": true,
    "insertedIds": {
        "0": ObjectId("..."),
        "1": ObjectId("..."),
        "2": ObjectId("..."),
        "3": ObjectId("..."),
        "4": ObjectId("...")
    }
}

View Sample Data

db.demo114.find();

{ "_id": ObjectId("..."), "Score": 60, "Name": "Chris" }
{ "_id": ObjectId("..."), "Score": 87, "Name": "Chris" }
{ "_id": ObjectId("..."), "Score": 45, "Name": "David" }
{ "_id": ObjectId("..."), "Score": 67, "Name": "Chris" }
{ "_id": ObjectId("..."), "Score": 38, "Name": "David" }

Find Maximum Score by Name

db.demo114.aggregate([
    {
        $group: {
            _id: "$Name",
            maximumScore: { $max: "$Score" }
        }
    }
]);

[
    { "_id": "Chris", "maximumScore": 87 },
    { "_id": "David", "maximumScore": 45 }
]

Alternative Method: Using group() (Legacy)

The legacy group() method can also be used, though aggregation pipeline is recommended ?

db.demo114.group({
    key: { Name: true },
    reduce: function(current, previous) {
        if (previous.maximumScore < current.Score) {
            previous.maximumScore = current.Score;
        }
    },
    initial: { maximumScore: 0 }
});

Key Points

• $group groups documents by the specified field (_id: "$Name").
• $max finds the maximum value within each group efficiently.
• Aggregation pipeline is preferred over the legacy group() method.

Conclusion

Use $group with $max in an aggregation pipeline to find maximum scores for duplicate names. This approach is efficient and follows modern MongoDB best practices.