Execute the following script in Query Editor to find the top 10 salesperson for each product(group). The ROW_NUMBER function creates a sequence number in descending sales order for each product in the CTE. The main SELECT takes the first 10 in each subset for the final report:

USE AdventureWorks;

WITH cteTop10Sales
AS
(SELECT ROW_NUMBER() OVER (PARTITION BY sod.ProductID ORDER BY SUM(sod.LineTotal) DESC) As SeqNo
, FirstName +' '+LastName AS [Name]
, ProductName = p.Name

, '$'+convert(varchar,convert(money,SUM(sod.LineTotal)),1) AS TotalBySalesPerson
, p.ProductNumber
, sod.ProductID
FROM Sales.SalesOrderDetail AS sod
INNER JOIN Production.Product AS p
ON sod.ProductID = p.ProductID
INNER JOIN Sales.SalesOrderHeader soh
ON sod.SalesOrderID = soh.SalesOrderID
INNER JOIN Person.Contact c
ON soh.SalesPersonID = c.ContactID
WHERE soh.SalesPersonID IS NOT NULL
GROUP BY FirstName +' '+LastName, sod.ProductID, p.ProductNumber, p.Name)

SELECT *
FROM cteTop10Sales cte
WHERE SeqNo <= 10
ORDER BY ProductID, SeqNo
GO