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Get the average of marks in MongoDB with aggregate?
Use $avg operator along with aggregate framework. Let us first create a collection with documents. Here, one of the fields is StudentScore −
> db.averageReturiningNullDemo.insertOne(
{"StudentDetails" : { "StudentScore" : 89 }
});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce9822e78f00858fb12e927")
}
> db.averageReturiningNullDemo.insertOne(
{"StudentDetails" : { "StudentScore" : 34 }
});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce9822e78f00858fb12e928")
}
> db.averageReturiningNullDemo.insertOne(
{"StudentDetails" : { "StudentScore" : 78 }
});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ce9822e78f00858fb12e929")
}Following is the query to display all documents from a collection with the help of find() method −
> db.averageReturiningNullDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5ce9822e78f00858fb12e927"),
"StudentDetails" : {
"StudentScore" : 89
}
}
{
"_id" : ObjectId("5ce9822e78f00858fb12e928"),
"StudentDetails" : {
"StudentScore" : 34
}
}
{
"_id" : ObjectId("5ce9822e78f00858fb12e929"),
"StudentDetails" : {
"StudentScore" : 78
}
}Following is the query to average returning −
> db.averageReturiningNullDemo.aggregate([
{
"$group": {
"_id": null,
"StudentScoreAverage": {
"$avg": "$StudentDetails.StudentScore"
}
}
}
]);This will produce the following output −
{ "_id" : null, "StudentScoreAverage" : 67 }
Updated on: 30-Jul-2019
274 Views
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