Calculate frequency of duplicate names from NAME field using MongoDB aggregate?

To calculate the frequency of duplicate names in MongoDB, use the $group stage in the aggregation pipeline to group documents by the Name field and count occurrences with $sum.

Syntax

db.collection.aggregate([
    { $group: { "_id": "$fieldName", count: { $sum: 1 } } }
]);

Create Sample Data

db.demo635.insertMany([
    {Name: "Chris"},
    {Name: "David"},
    {Name: "David"},
    {Name: "Chris"},
    {Name: "Bob"},
    {Name: "Chris"}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e9c10f06c954c74be91e6cc"),
        ObjectId("5e9c10f46c954c74be91e6cd"),
        ObjectId("5e9c10f66c954c74be91e6ce"),
        ObjectId("5e9c10f86c954c74be91e6cf"),
        ObjectId("5e9c10fb6c954c74be91e6d0"),
        ObjectId("5e9c10fc6c954c74be91e6d1")
    ]
}

Display Sample Data

db.demo635.find();

{ "_id" : ObjectId("5e9c10f06c954c74be91e6cc"), "Name" : "Chris" }
{ "_id" : ObjectId("5e9c10f46c954c74be91e6cd"), "Name" : "David" }
{ "_id" : ObjectId("5e9c10f66c954c74be91e6ce"), "Name" : "David" }
{ "_id" : ObjectId("5e9c10f86c954c74be91e6cf"), "Name" : "Chris" }
{ "_id" : ObjectId("5e9c10fb6c954c74be91e6d0"), "Name" : "Bob" }
{ "_id" : ObjectId("5e9c10fc6c954c74be91e6d1"), "Name" : "Chris" }

Calculate Name Frequency

Group documents by Name field and count occurrences using the aggregation framework ?

db.demo635.aggregate([
    { $group: { "_id": "$Name", TotalFrequency: { $sum: 1 } } }
]);

{ "_id" : "David", "TotalFrequency" : 2 }
{ "_id" : "Bob", "TotalFrequency" : 1 }
{ "_id" : "Chris", "TotalFrequency" : 3 }

Key Points

• The $group stage groups documents by the specified field ($Name).
• $sum: 1 increments the counter for each document in the group.
• The _id field in the output contains the grouped field value.

Conclusion

Use MongoDB's $group aggregation stage with $sum: 1 to efficiently calculate the frequency of duplicate values in any field. This approach groups identical values and counts their occurrences in a single query.