How to select a field and a count of a nested array in mongodb [duplicate]

Question

I have the following mongo db collection

{
 "_id" : 1,
 "name" : "Sam",
 "telephone" : [1234,4567,8678],
 "age" : 34
},
{
 "_id" : 2,
 "name" : "Joe",
 "telephone" : [4456,4434],
 "age" : 42
}

I want to fetch the name and the count of telephone. what should be the query? My output should be as below.

{
  "name" : "Sam",
  "telephoneCount" : 3
},
{
  "name" : "Joe",
  "telephoneCount" : 2
}

Zeeshan Ashraf · Accepted Answer · 2023-03-04 18:36:54Z

17

You can use the below query. Use $project to keep the name field and $size to count the telephone numbers.

db.collection.aggregate([
{
                $project: {
                    name: name,
                    telephoneCount: { $size: '$telephone' },
                },
            }
]);

edited Mar 4, 2023 at 18:36

Zeeshan Ashraf

33 bronze badges

answered Apr 30, 2017 at 17:28

s7vr

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