string concatenate in group by function with other aggregate functions

Question

Is it possible to concatenate strings with one or more of other group by function like sum, avg, count etc .

Say I have the following table

Id Name O         


        

Answer 1

If you're using MS SQL Server 2005 or newer you can create user-defined aggregate functions.

MSDN: CREATE AGGREGATE (Transact-SQL)

MSDN: Invoking CLR User-Defined Aggregate Functions