Select * group by in mongo aggregation

Question

I am trying to do something that I think is quite simple. Suppose I have a series of records in mongo that have a common key, and variable number of attributes. I want to select

Answer 1

If you want to combine the attributes, you'll need to add those to the group. For example, using $addToSet to find the unique values of the x,y,z attributes grouped by each name:

db.data.aggregate(
    { $group : {
            _id : "$Name",
            x: { $addToSet: "$x" },
            y: { $addToSet: "$y" },
            z: { $addToSet: "$z" },
    }}
)

Returns:

{
    "result" : [
        {
            "_id" : "Rob",
            "x" : [
                12
            ],
            "y" : [
                2
            ],
            "z" : [ ]
        },
        {
            "_id" : "George",
            "x" : [
                5
            ],
            "y" : [
                3
            ],
            "z" : [
                9
            ]
        }
    ],
    "ok" : 1
}