SELECT 
      CategoryName,  
      SUM(UnitPrice) as UnitPrice,  
      SUM(UnitsinStock) as UnitsinStock  
FROM Products 
    INNER JOIN Categories On 
   Products.CategoryID = Categories.CategoryID 
GROUP BY CategoryName

SELECT
  CASE 
    WHEN (Grouping(CategoryName)=1) THEN 'MainTotal' 
    ELSE CategoryName 
  END AS CategoryName, 

  CASE 
    WHEN (Grouping(ProductName)=1) THEN 'SubTotal' 
    ELSE Productname 
  END AS ProductName,  

  Sum(UnitPrice) as UnitPrice,  
  Sum(UnitsinStock) as UnitsInStock  

FROM Products 
  INNER JOIN Categories On 
       Products.CategoryID = Categories.CategoryID 
GROUP BY CategoryName, ProductName WITH ROLLUP