CODEWITHSUNDEEP
mongodb
mp1990
mp1990

Reputation: 10239

Getting distinct values from object array MongoDB

{
    "_id" : NUUID("f5050a5d-b3be-4de6-a135-a119436fb511"),
    "CoursesData" : [ 
        {
            "Name" : "Naturgræs",
            "Value" : 1
        }
    ],
    "FacilityType" : {
        "_id" : NUUID("a1b4844b-518b-40e2-8aa5-8ee399ac2d4e")
    }
}

I want to retrieve a list with the distinct values from the field Name inside my object array of CourseData. Filtered by FacilityType._id. I tried using both $facet and the distinct operator, but it doesn't seems to like object arrays.

My result should look like this (or similar):

FacilityType (a1b4844b-518b-40e2-8aa5-8ee399ac2d4e),
CourseData: [Name1, Name2, Name3]

Update

From the answer given below, this is how you do it with the C# driver, if anyone needs to do the same.

  FieldDefinition<FacilityDocument, string> field = "CoursesData.Name";

  var result = FacilityCollection.Distinct(field, Builders<FacilityDocument>.Filter.Eq(x => x.FacilityType.ID, new Guid("a1b4844b-518b-40e2-8aa5-8ee399ac2d4e"))).ToList();

Upvotes: 3

Views: 5658

Answers (1)

felix
felix

Reputation: 9285

You can use distinct(). It will return distinct element for a specific field from document which match a query

For example if you want distinct value of Name field for facility "a1b4844b-518b-40e2-8aa5-8ee399ac2d4e", run this query: 

db.collection.distinct("CoursesData.Name", {"FacilityType._id": "a1b4844b-518b-40e2-8aa5-8ee39ac2d4e"})

it will return : 

[ "Naturgræs", ... ]

Upvotes: 4

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