Perform min/max with MongoDB aggregation

For min/max in MongoDB, use $min and $max. Let us create a collection with documents −

> db.demo251.insertOne({"Marks":78});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e46c0001627c0c63e7dba74")
}
> db.demo251.insertOne({"Marks":87});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e46c0031627c0c63e7dba75")
}
> db.demo251.insertOne({"Marks":56});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e46c0061627c0c63e7dba76")
}
> db.demo251.insertOne({"Marks":76});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e46c00c1627c0c63e7dba77")
}

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

> db.demo251.find();

This will produce the following output −

{ "_id" : ObjectId("5e46c0001627c0c63e7dba74"), "Marks" : 78 }
{ "_id" : ObjectId("5e46c0031627c0c63e7dba75"), "Marks" : 87 }
{ "_id" : ObjectId("5e46c0061627c0c63e7dba76"), "Marks" : 56 }
{ "_id" : ObjectId("5e46c00c1627c0c63e7dba77"), "Marks" : 76 }

Following is the query to implement min/max aggregation in MongoDB −

> db.demo251.aggregate([
...   { "$group": {
...      "_id": null,
...      "MaxMarks": { "$max": "$Marks" },
...      "MinMarks": { "$min": "$Marks" }
...   }}
...])

This will produce the following output −

{ "_id" : null, "MaxMarks" : 87, "MinMarks" : 56 }