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Limit number of values in a field with MongoDB?
To limit the number of values in a field, use MongoDB $slice. Let us create a collection with documents −
> db.demo173.insertOne({"ListOfValues":[10,40,100,560,700,900]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e383a4f9e4f06af551997e4")
}Display all documents from a collection with the help of find() method −
> db.demo173.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5e383a4f9e4f06af551997e4"),
"ListOfValues" : [10, 40, 100, 560, 700, 900 ]
}Following is the query to limit number of values in a field using MongoDB −
> db.demo173.find({}, { "ListOfValues": { "$slice": -2 } } );This will produce the following output −
{ "_id" : ObjectId("5e383a4f9e4f06af551997e4"), "ListOfValues" : [ 700, 900 ] }
Updated on: 27-Mar-2020
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