Group on multiple fields

[Doug_Duncan]

Hi @Helene_ORTIZ, and welcome to the community forums.

@Helene_ORTIZ

And how do I add fields in my $group operator ?

To group on multiple fields in an aggregation, you would make the _id field an object like the following:

{
    $group: {
        "_id": {
            ctype: "$ctype",
            cname: "$cname",
            pname: "$pname"
        },
        ...
    }
}

this will give you a grouping for each unique combination of values in those three fields.

@Helene_ORTIZ

In the “output after $group stage” window, there is the following result:

_id: “Axis”

while I have three different ctype values in my collection.

Without seeing the data, query and results it’s hard to say why you only got a single value back if you have three unique values in the dataset for ctype.