MongoDB এ অ্যাগ্রিগেট ফাংশন বাস্তবায়ন করার কোয়েরি

প্রথমে ডকুমেন্টসহ একটি কলেকশন তৈরি করি:

> db.demo121.insertOne(
    {
        "Id" : 101,
        "Details" : [
            {
                "SubjectId" : "1",
                "SubjectName" : "MongoDB",
                "Score" : 76
            },
            {
                "SubjectId" : "2",
                "SubjectName" : "MySQL",
                "Score" : 76
            },
            {
                "SubjectId" : "3",
                "SubjectName" : "Java",
                "Score" : 76
            }
        ]
    }
);
{ "acknowledged" : true, "insertedId" : ObjectId("5e2f1c60140daf4c2a3544b3") }

find() মেথড দিয়ে কলেকশন থেকে সব ডকুমেন্ট দেখান:

> db.demo121.find();

আউটপুট:

{ "_id" : ObjectId("5e2f1c60140daf4c2a3544b3"), "Id" : 101, "Details" : [ { "SubjectId" : "1", "SubjectName" : "MongoDB", "Score" : 76 }, { "SubjectId" : "2", "SubjectName" : "MySQL", "Score" : 76 }, { "SubjectId" : "3", "SubjectName" : "Java", "Score" : 76 } ] }

অ্যাগ্রিগেট ফাংশন বাস্তবায়নের কোয়েরি:

> db.demo121.aggregate([
    { "$match": { "Id": 101 } },
    { "$unwind": "$Details" },
    {
        "$group": {
            "_id": "$Details.SubjectId",
            "count": { "$sum": 1 },
            "Details": {
                "$push": {
                    "SubjectName": "$Details.SubjectName"
                }
            }
        }
    },
    {
        "$group": {
            "_id": null,
            "List": {
                "$push": {
                    "SubId": "$_id",
                    "Details": "$Details"
                }
            }
        }
    }
], function (err, out) {
    res.json(out);
});

ফলাফল:

{ "_id" : null, "List" : [ { "SubId" : "3", "Details" : [ { "SubjectName" : "Java" } ] }, { "SubId" : "2", "Details" : [ { "SubjectName" : "MySQL" } ] }, { "SubId" : "1", "Details" : [ { "SubjectName" : "MongoDB" } ] } ] }