Write a MongoDB aggregation query to group and calculate the average of a field in a collection.

Question

Aryan Kumar · Answer

Sure, here is a MongoDB aggregation to group and calculate the average of a field in a collection:

db.collection.aggregate([
  {
    $group: {
      _id: "$field",
      average: {
        $avg: "$field"
      }
    }
  }
]);

This aggregation will group the documents in the collection by the value of the field field. For each group, the average of the field field will be calculated and stored in the average field.

For example, if the collection contains the following documents:

{ "field": 10 }
{ "field": 20 }
{ "field": 30 }

The aggregation will produce the following output:

{ "_id": 10, "average": 15 }
{ "_id": 20, "average": 20 }
{ "_id": 30, "average": 30 }

The _id field in the output documents is the value of the field field in the original documents. The average field is the average of the field field in the documents that were grouped together.

To run this aggregation, you can use the mongo shell or a MongoDB driver. For example, to run the aggregation using the mongo shell, you would use the following command:

mongo <database> <collection> --eval "db.collection.aggregate([{ $group: { _id: '$field', average: { $avg: '$field' } } }])"

Replace <database> and <collection> with the name of the database and collection that you want to use.

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Write a MongoDB aggregation query to group and calculate the average of a field in a collection.

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