Perform group and distinct together in a single MongoDB query

MongoDBDatabaseBig Data Analytics

For this, simply use MongoDB $group. Let us first create a collection with documents −

> db.demo16.insertOne({
...    "StudentName" : "Chris",
...    "StudentSection" : "A",
...    "StudentAge" : 23,
...    "StudentMarks" : 47
... }
... );
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e13827455d0fc6657d21f07")
}
> db.demo16.insertOne({
...    "StudentName" : "Bob",
...    "StudentSection" : "B",
...    "StudentAge" : 21,
...    "StudentMarks" : 85
... }
... );
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e13827555d0fc6657d21f08")
}
> db.demo16.insertOne( {
...    "StudentName" : "Carol",
...    "StudentSection" : "A",
...    "StudentAge" : 26,
...    "StudentMarks" : 97
... }
... );
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e13827655d0fc6657d21f09")
}

Following is the query to display all documents from a collection with the help of find() method −

> db.demo16.find().pretty();

This will produce the following output −

{
   "_id" : ObjectId("5e13827455d0fc6657d21f07"),
   "StudentName" : "Chris",
   "StudentSection" : "A",
   "StudentAge" : 23,
   "StudentMarks" : 47
}
{
   "_id" : ObjectId("5e13827555d0fc6657d21f08"),
   "StudentName" : "Bob",
   "StudentSection" : "B",
   "StudentAge" : 21,
   "StudentMarks" : 85
}
{
   "_id" : ObjectId("5e13827655d0fc6657d21f09"),
   "StudentName" : "Carol",
   "StudentSection" : "A",
   "StudentAge" : 26,
   "StudentMarks" : 97
}

Following is the query to implement group and distinct operation together −

> db.demo16.aggregate([{
...    $group : {
...       _id : null,
...       StudentName : { $addToSet : "$StudentName" },
...       StudentSection : { $addToSet : "$StudentSection" },
...       StudentMinimumAge : { $min : "$StudentAge" },
...       StudentMaximumAge : { $max : "$StudentAge" },
...       StudentMinimumMarks: { $min : "$StudentMarks" },
...       StudentMaximumMarks : { $max : "$StudentMarks" }
... }
... }]).pretty();

This will produce the following output −

{
   "_id" : null,
      "StudentName" : [
         "Carol",
         "Bob",
         "Chris"
      ],
   "StudentSection" : [
      "B",
      "A"
   ],
   "StudentMinimumAge" : 21,
   "StudentMaximumAge" : 26,
   "StudentMinimumMarks" : 47,
   "StudentMaximumMarks" : 97
}
raja
Published on 01-Apr-2020 14:24:31
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