Count distinct value in Array in mongodb

Question

Sample Doc :


{
    "id": "K",
    "powers": [
        {
            "label": "a",
            "Rating": 7
        },
        {
            "label": "b",
            "Rating": 3
        },
        {
            "label": "c",
            "Rating": 4
        },
        {
            "label": "d",
            "Rating": 5
        }
    ],
    "phy": {
        "height": 67,
        "weight": 150
    }
}

For this collection, I want to count how many distinct powers each id has.

I want the result as - ID =K, distinct power label - 4

Does this answer your question? [Get distinct records values](https://stackoverflow.com/questions/20655506/get-distinct-records-values) — whoami - fakeFaceTrueSoul, Apr 20 '20 at 00:19

score 0 · Answer 1 · answered Apr 19 '20 at 22:17

0

So the easiest way to get it done is

/** db.collection.distinct('field on which distinct is needed', condition) */

db.collection.distinct('powers.label', {"id" : "K"})

As it will be an array, You can do .length in code to get the unique length.

Ref : .distinct()

answered Apr 19 '20 at 22:17

whoami - fakeFaceTrueSoul

17,086
6
32
46

Can you please show with length for all ID's . Two columns - ID , Length ( number of powers) – kbs Apr 19 '20 at 23:09
@Kulbirsingh : What do you men *show with length for all ID's* ? – whoami - fakeFaceTrueSoul Apr 20 '20 at 00:20

Count distinct value in Array in mongodb

1 Answers1