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To perform aggregation operations with MongoDB, you need to have a good understanding of the aggregation pipeline stages. This tutorial will explore $sortthe stages through an example to perform a MongoDB aggregation sort.

MongoDB Aggregate Sorting

Let's have a scenario to practice the code examples. We have a studentcollection called which contains basic information.

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Sample code:

> db.createCollection('student');
> db.student.insertMany([
    {"student_code": "ma001", "name": "Mehvish Ashiq", "postcode": 2000},
    {"student_code": "tc002", "name": "Thomas Christopher", "postcode": 2001},
    {"student_code": "km003", "name": "Krishna Mehta", "postcode": 2000},
    {"student_code": "ar004", "name": "Aftab Raza", "postcode": 2000},
    {"student_code": "za005", "name": "Zeenat Ashraf", "postcode": 2002},
    {"student_code": "ka006", "name": "Kanwal Ali", "postcode": 2002}
]);
> db.student.find().pretty();

Output:

{
        "_id" : ObjectId("629afe5a0a3b0e96fe92e97b"),
        "student_code" : "ma001",
        "name" : "Mehvish Ashiq",
        "postcode" : 2000
}
{
        "_id" : ObjectId("629afe5a0a3b0e96fe92e97c"),
        "student_code" : "tc002",
        "name" : "Thomas Christopher",
        "postcode" : 2001
}
{
        "_id" : ObjectId("629afe5a0a3b0e96fe92e97d"),
        "student_code" : "km003",
        "name" : "Krishna Mehta",
        "postcode" : 2000
}
{
        "_id" : ObjectId("629afe5a0a3b0e96fe92e97e"),
        "student_code" : "ar004",
        "name" : "Aftab Raza",
        "postcode" : 2000
}
{
        "_id" : ObjectId("629afe5a0a3b0e96fe92e97f"),
        "student_code" : "za005",
        "name" : "Zeenat Ashraf",
        "postcode" : 2002
}
{
        "_id" : ObjectId("629afe5a0a3b0e96fe92e980"),
        "student_code" : "ka006",
        "name" : "Kanwal Ali",
        "postcode" : 2002
}

Next, we want to determine the class that holds the maximum number of students but in a sorted form postcode. To do this, check the following sample code.

Sample code:

> db.student.aggregate([
    { $group: { _id: '$postcode', students: { $sum: 1 } } },
    { $sort: {_id: 1} }
]);

Output:

{ "_id" : 2000, "students" : 3 }
{ "_id" : 2001, "students" : 1 }
{ "_id" : 2002, "students" : 2 }

Here, we use aggregate()the function to calculate the aggregate value of the data in the specified collection or view . In aggregate()the method, we postcodegroup the documents based on the field.

Furthermore, we postcodereturn as _id, where students are postcodecounted for each students. Here, we use $sumto get postcodethe number of students for each .

$sumComputes and returns the sum of numeric values ​​by ignoring non-numeric values.

Finally, we use $sortphase to sort them in ascending or descending order based on the project needs. 1is used for ascending order, while -1is used for descending order.