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Get the aggregated result and find the count of repeated values in different MongoDB\\ndocuments
To get the count of repeated values in different documents, use aggregate(). Let us create a collection with documents −
> db.demo452.insertOne({"StudentName":"John","StudentAge":21});{
"acknowledged" : true,
"insertedId" : ObjectId("5e7b7e3371f552a0ebb0a6f3")
}
> db.demo452.insertOne({"StudentName":"John","StudentAge":22});{
"acknowledged" : true,
"insertedId" : ObjectId("5e7b7e3671f552a0ebb0a6f4")
}
> db.demo452.insertOne({"StudentName":"John","StudentAge":23});{
"acknowledged" : true,
"insertedId" : ObjectId("5e7b7e3971f552a0ebb0a6f5")
}
> db.demo452.insertOne({"StudentName":"David","StudentAge":24});{
"acknowledged" : true,
"insertedId" : ObjectId("5e7b7e4371f552a0ebb0a6f6")
}
> db.demo452.insertOne({"StudentName":"David","StudentAge":25});{
"acknowledged" : true,
"insertedId" : ObjectId("5e7b7e4571f552a0ebb0a6f7")
}
Display all documents from a collection with the help of find() method −
> db.demo452.find();
This will produce the following output −
{ "_id" : ObjectId("5e7b7e3371f552a0ebb0a6f3"), "StudentName" : "John", "StudentAge" : 21 }
{ "_id" : ObjectId("5e7b7e3671f552a0ebb0a6f4"), "StudentName" : "John", "StudentAge" : 22 }
{ "_id" : ObjectId("5e7b7e3971f552a0ebb0a6f5"), "StudentName" : "John", "StudentAge" : 23 }
{ "_id" : ObjectId("5e7b7e4371f552a0ebb0a6f6"), "StudentName" : "David", "StudentAge" : 24}
{ "_id" : ObjectId("5e7b7e4571f552a0ebb0a6f7"), "StudentName" : "David", "StudentAge" : 25}
Following is the query to find the count of repeated values in different MongoDB documents −
> db.demo452.aggregate([
... {$group: {_id:"$StudentName", count:{$sum:1}}},
... {$sort: {count:-1}},
...
... {$group: {_id:1, StudentName:{$push:{StudentName:"$_id", count:"$count"}}}},
... {$project: {
... first : {$arrayElemAt: ["$StudentName", 0]},
... second: {$arrayElemAt: ["$StudentName", 1]},
... others: {$slice:["$StudentName", 2, {$size: "$StudentName"}]}
... }
... },
...
... {$project: {
... status: [
... "$first",
... "$second",
... {
... StudentName: "New Student Name",
... count: {$sum: "$others.count"}
... }
... ]
... }
... },
...
... {$unwind: "$status"},
... {$project: { _id:0, StudentName: "$status.StudentName", count: "$status.count" }}
... ])
This will produce the following output −
{ "StudentName" : "John", "count" : 3 }
{ "StudentName" : "David", "count" : 2 }
{ "StudentName" : "New Student Name", "count" : 0 }
Updated on: 2020-05-11T09:11:28+05:30
170 Views
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