Syntax error MongoDB Group query to get the count of repeated marks in documents?

MongoDB Group query to get the count of repeated marks in documents?

For group query, use MongoDB $group and get the count with $sum. Let us create a collection with documents −

> db.demo676.insertOne({"Marks":87});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ea41eed04263e90dac943f2")
}
> db.demo676.insertOne({"Marks":75});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ea41ef304263e90dac943f3")
}
> db.demo676.insertOne({"Marks":87});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ea41ef404263e90dac943f4")
}
> db.demo676.insertOne({"Marks":65});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ea41ef704263e90dac943f5")
}
> db.demo676.insertOne({"Marks":65});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ea41ef804263e90dac943f6")
}

Display all documents from a collection with the help of find() method −

> db.demo676.find();

This will produce the following output −

{ "_id" : ObjectId("5ea41eed04263e90dac943f2"), "Marks" : 87 }
{ "_id" : ObjectId("5ea41ef304263e90dac943f3"), "Marks" : 75 }
{ "_id" : ObjectId("5ea41ef404263e90dac943f4"), "Marks" : 87 }
{ "_id" : ObjectId("5ea41ef704263e90dac943f5"), "Marks" : 65 }
{ "_id" : ObjectId("5ea41ef804263e90dac943f6"), "Marks" : 65 }

Following is the query to get the count of repeated marks −

> db.demo676.aggregate( { $group: {
...    _id: {Marks: "$Marks" },
...    'Count': { $sum :1 }
... }})

This will produce the following output −

{ "_id" : { "Marks" : 75 }, "Count" : 1 }
{ "_id" : { "Marks" : 65 }, "Count" : 2 }
{ "_id" : { "Marks" : 87 }, "Count" : 2 }
Updated on: 2020-05-13T10:06:36+05:30

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