mongodbHow to group in MongoDB?

MongoDB provides the $group aggregation operator to group documents by a specified key and perform accumulator operations.

Example

db.collection.aggregate([
    {
        $group: {
            _id: "$department",
            totalSalary: { $sum: "$salary" }
        }
    }
])

Output example

{ "_id" : "IT", "totalSalary" : 30000 }
{ "_id" : "HR", "totalSalary" : 15000 }

The $group operator has the following parts:

• _id: The key to group documents by.
• totalSalary: The accumulator expression to perform operations on the grouped documents.

Helpful links

• MongoDB Aggregation

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