Is Group By Supported?

[Brendan Enrick]

Is to possible to use a group by statement to get data grouped by certain values and have that translated into the SQL so that the grouping is performed before coming back to the application?

[Damyan Bogoev]

Hi Brendan Enrick,

Yes, Telerik OpenAccess ORM translates the group by statement into a sql query and the grouping is performed by the database server. For example, the following statement is executed on the server:

var q = from o in scope.Extent<Order>()
        group o by o.OrderDate into g
        select g;

Unfortunately, server-side grouping could not be performed currently on non-nullable fields (value-type fields). This is scheduled for fixing and should be available in the upcoming service pack release.

In the meantime, if you need to perform grouping on a non-nullable field, this could be done on the client by using the ToList() method. It forces the execution of the query and the grouping is done afterwards in memory:

var q = from o in scope.Extent<Order>().ToList()
        group o by o.OrderDate into g
        select g;

Kind regards,
Damyan Bogoev
the Telerik team

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[Patrice Boissonneault]

What would this look like with the new context model?  Also, how to aggregate?
Thanks.

[Damyan Bogoev]

Hi Patrice,

You should slightly modify the code snippet in order to use the Linq query with the new domain model:

YourContextName context = new YourContextName();
var q = from o in context.Orders
        group o by o.OrderDate into g
        select g;

Helpful sample aggregate Linq queries example can be found in the Product SDK. Hope you will find it useful.

If any other questions arise, do not hesitate to contact us back.

Kind regards,
Damyan Bogoev
the Telerik team