MongoDB query to limit the returning values of a field?

For this, use $slice. Let us create a collection with documents −

> db.demo594.insertOne(
...    {
...       id:1,
...       details:[
...          {Name:"Chris",Age:21},
...          {Name:"Bob",Age:20},
...          {Name:"David",Age:23},
...          {Name:"Sam",Age:22}
...       ]
...    }
... );
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e933459fd2d90c177b5bcdd")
}

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

> db.demo594.find();

This will produce the following output −

{ "_id" : ObjectId("5e933459fd2d90c177b5bcdd"), "id" : 1, "details" : [
   { "Name" : "Chris", "Age" : 21 },
   { "Name" : "Bob", "Age" : 20 },
   { "Name" : "David", "Age" : 23 },
   { "Name" : "Sam", "Age" : 22 }
] }

Following is the query to limit the returning values of a field −

> db.demo594.find({}, {"Name": 1, "details": { "$slice": 1}});

This will produce the following output −

{ "_id" : ObjectId("5e933459fd2d90c177b5bcdd"), "details" : [
   { "Name" : "Chris", "Age" : 21 } 
] }

AmitDiwan

Published on 15-May-2020 10:27:32