Count distinct in mongodb not giving distinct results












1














a proper sql guy struggling with no-sql:



i am looking for an alternative in mongodb for a query like



select city, count(distinct device) from collection group by city, devicetype



My collection is like



{
"city":"city1",
"device": "device1"
"deviceType":1
},
{
"city":"city1",
"device": "device2"
"deviceType":0
},
{
"city":"city1",
"device": "device3"
"deviceType":1
},
{
"city":"city1",
"device": "device2"
"deviceType":0
}


After grouping, i need distinct devices used by their devicetype of each city



means, the output would be like



{
"city":"city1",
"deviceType":0,
"deviceCount":1 //device2
},
{
"city":"city1",
"deviceType":1,
"deviceCount":2 //device1, device3
}


I tried



"$group": {
_id: { "city": "$city", "devicetype": "$devicetype" },
"devicetype": { "$first": "$devicetype" },
"count": { "$sum": 1 }
}


I am getting the total count of devices, not the distinct count.



please suggest!!










share|improve this question




















  • 2




    stackoverflow.com/questions/24761266/… read last answer.
    – Sameer
    Nov 21 '18 at 12:30


















1














a proper sql guy struggling with no-sql:



i am looking for an alternative in mongodb for a query like



select city, count(distinct device) from collection group by city, devicetype



My collection is like



{
"city":"city1",
"device": "device1"
"deviceType":1
},
{
"city":"city1",
"device": "device2"
"deviceType":0
},
{
"city":"city1",
"device": "device3"
"deviceType":1
},
{
"city":"city1",
"device": "device2"
"deviceType":0
}


After grouping, i need distinct devices used by their devicetype of each city



means, the output would be like



{
"city":"city1",
"deviceType":0,
"deviceCount":1 //device2
},
{
"city":"city1",
"deviceType":1,
"deviceCount":2 //device1, device3
}


I tried



"$group": {
_id: { "city": "$city", "devicetype": "$devicetype" },
"devicetype": { "$first": "$devicetype" },
"count": { "$sum": 1 }
}


I am getting the total count of devices, not the distinct count.



please suggest!!










share|improve this question




















  • 2




    stackoverflow.com/questions/24761266/… read last answer.
    – Sameer
    Nov 21 '18 at 12:30
















1












1








1







a proper sql guy struggling with no-sql:



i am looking for an alternative in mongodb for a query like



select city, count(distinct device) from collection group by city, devicetype



My collection is like



{
"city":"city1",
"device": "device1"
"deviceType":1
},
{
"city":"city1",
"device": "device2"
"deviceType":0
},
{
"city":"city1",
"device": "device3"
"deviceType":1
},
{
"city":"city1",
"device": "device2"
"deviceType":0
}


After grouping, i need distinct devices used by their devicetype of each city



means, the output would be like



{
"city":"city1",
"deviceType":0,
"deviceCount":1 //device2
},
{
"city":"city1",
"deviceType":1,
"deviceCount":2 //device1, device3
}


I tried



"$group": {
_id: { "city": "$city", "devicetype": "$devicetype" },
"devicetype": { "$first": "$devicetype" },
"count": { "$sum": 1 }
}


I am getting the total count of devices, not the distinct count.



please suggest!!










share|improve this question















a proper sql guy struggling with no-sql:



i am looking for an alternative in mongodb for a query like



select city, count(distinct device) from collection group by city, devicetype



My collection is like



{
"city":"city1",
"device": "device1"
"deviceType":1
},
{
"city":"city1",
"device": "device2"
"deviceType":0
},
{
"city":"city1",
"device": "device3"
"deviceType":1
},
{
"city":"city1",
"device": "device2"
"deviceType":0
}


After grouping, i need distinct devices used by their devicetype of each city



means, the output would be like



{
"city":"city1",
"deviceType":0,
"deviceCount":1 //device2
},
{
"city":"city1",
"deviceType":1,
"deviceCount":2 //device1, device3
}


I tried



"$group": {
_id: { "city": "$city", "devicetype": "$devicetype" },
"devicetype": { "$first": "$devicetype" },
"count": { "$sum": 1 }
}


I am getting the total count of devices, not the distinct count.



please suggest!!







mongodb mongodb-query aggregation-framework






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 23 '18 at 10:37









Anthony Winzlet

13.9k41239




13.9k41239










asked Nov 21 '18 at 11:48









Lakshman Pilaka

6472722




6472722








  • 2




    stackoverflow.com/questions/24761266/… read last answer.
    – Sameer
    Nov 21 '18 at 12:30
















  • 2




    stackoverflow.com/questions/24761266/… read last answer.
    – Sameer
    Nov 21 '18 at 12:30










2




2




stackoverflow.com/questions/24761266/… read last answer.
– Sameer
Nov 21 '18 at 12:30






stackoverflow.com/questions/24761266/… read last answer.
– Sameer
Nov 21 '18 at 12:30














1 Answer
1






active

oldest

votes


















1














You can use below aggregation



db.collection.aggregate([
{ "$group": {
_id: {
"city": "$city",
"deviceType": "$deviceType"
},
"deviceCount": { "$addToSet": "$device" },
"count": { "$sum": 1 }
}},
{ "$project": {
"_id": 0,
"city": "$_id.city",
"deviceType": "$_id.deviceType",
"deviceCount": { "$size": "$deviceCount" }
}}
])


Output



[
{
"city": "city1",
"deviceCount": 1,
"deviceType": 0
},
{
"city": "city1",
"deviceCount": 2,
"deviceType": 1
}
]





share|improve this answer





















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    1 Answer
    1






    active

    oldest

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    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    1














    You can use below aggregation



    db.collection.aggregate([
    { "$group": {
    _id: {
    "city": "$city",
    "deviceType": "$deviceType"
    },
    "deviceCount": { "$addToSet": "$device" },
    "count": { "$sum": 1 }
    }},
    { "$project": {
    "_id": 0,
    "city": "$_id.city",
    "deviceType": "$_id.deviceType",
    "deviceCount": { "$size": "$deviceCount" }
    }}
    ])


    Output



    [
    {
    "city": "city1",
    "deviceCount": 1,
    "deviceType": 0
    },
    {
    "city": "city1",
    "deviceCount": 2,
    "deviceType": 1
    }
    ]





    share|improve this answer


























      1














      You can use below aggregation



      db.collection.aggregate([
      { "$group": {
      _id: {
      "city": "$city",
      "deviceType": "$deviceType"
      },
      "deviceCount": { "$addToSet": "$device" },
      "count": { "$sum": 1 }
      }},
      { "$project": {
      "_id": 0,
      "city": "$_id.city",
      "deviceType": "$_id.deviceType",
      "deviceCount": { "$size": "$deviceCount" }
      }}
      ])


      Output



      [
      {
      "city": "city1",
      "deviceCount": 1,
      "deviceType": 0
      },
      {
      "city": "city1",
      "deviceCount": 2,
      "deviceType": 1
      }
      ]





      share|improve this answer
























        1












        1








        1






        You can use below aggregation



        db.collection.aggregate([
        { "$group": {
        _id: {
        "city": "$city",
        "deviceType": "$deviceType"
        },
        "deviceCount": { "$addToSet": "$device" },
        "count": { "$sum": 1 }
        }},
        { "$project": {
        "_id": 0,
        "city": "$_id.city",
        "deviceType": "$_id.deviceType",
        "deviceCount": { "$size": "$deviceCount" }
        }}
        ])


        Output



        [
        {
        "city": "city1",
        "deviceCount": 1,
        "deviceType": 0
        },
        {
        "city": "city1",
        "deviceCount": 2,
        "deviceType": 1
        }
        ]





        share|improve this answer












        You can use below aggregation



        db.collection.aggregate([
        { "$group": {
        _id: {
        "city": "$city",
        "deviceType": "$deviceType"
        },
        "deviceCount": { "$addToSet": "$device" },
        "count": { "$sum": 1 }
        }},
        { "$project": {
        "_id": 0,
        "city": "$_id.city",
        "deviceType": "$_id.deviceType",
        "deviceCount": { "$size": "$deviceCount" }
        }}
        ])


        Output



        [
        {
        "city": "city1",
        "deviceCount": 1,
        "deviceType": 0
        },
        {
        "city": "city1",
        "deviceCount": 2,
        "deviceType": 1
        }
        ]






        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 21 '18 at 19:24









        Anthony Winzlet

        13.9k41239




        13.9k41239






























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