> Dear all
> My collections which have key is a array object.
> I need sum total as SQL statement:
>                    *Select Line_Items.Name , Sum(Line_Items.Quantity)
> from Orders group by Line_Items.Name*
> Could I use group to sum data instead of map/reduce?
> Please help me for this case ?

> Thanks

> My data samples

> db.Orders.find()
> {
>         "_id" : ObjectId("505057cbe415556238661561"),
>         "BuyerName" : "Lukas",
>         "Line_Items" : [
>                 {
>                         "Name" : "2012 Accord SeDan",
>                         "Pricing" : 20,
>                         "Quantity" : 1
>                 },
>                 {
>                         "ProductID" : ObjectId("50504b36e41555623866155c"),
>                         "Name" : "2012 Accord Coupe",
>                         "Pricing" : 15,
>                         "Quantity" : 2
>                 }
>         ],
>         "IssueDate" : ISODate("2012-03-08T00:00:00Z"),
>          "Total" : 50
> }

> ,

> {
>         "_id" : ObjectId("505057cbe415556238661560"),
>         "BuyerName" : "Bobby",
>         "Line_Items" : [
>                 {
>                         "Name" : "2012 Accord SeDan",
>                         "Pricing" : 15,
>                         "Quantity" : 1
>                 }
>         ],
>         "IssueDate" : ISODate("2012-02-08T00:00:00Z"),
>         "Total" : 15
> }

> Thanks and Regards.

> Tom Vo

> Hi Tom,

> You could use the Aggregation Framework in MongoDB 2.2 to sum the data by
> name:

> db.Orders.aggregate(
>   { $unwind: "$Line_Items" },
>   { $group : {
>  _id: "$Line_Items.Name",
>  Quantity: { $sum: "$Line_Items.Quantity"}
>   }}
> )

> There are a few limitations to be aware of, in particular that the output
> from the Aggregation Framework is limited to the maximum BSON document size
> (16Mb):
> http://docs.mongodb.org/manual/applications/aggregation/#limitations.

> You may also want to start your aggregation with an indexed $match to
> limit the range of documents to aggregate.

> > Have Mongodb support sum/avg key in array of Object by use Aggregation
> Group/Map Reduce yet?

> The new aggregation framework includes a number of mathematical functions
> such as $sum, $avg, $min, and $max:

> http://docs.mongodb.org/manual/reference/aggregation/#arithmetic-oper...

> Cheers,
> Stephen

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