with ProductClass(ClassId,ClassName) as

(

select ClassId,ClassName from Classes where ClassId = 31281

union all

select c.ClassId,c.ClassName from Classes c inner join ProductClass parent on c.ParentClassId = parent.ClassId

)

select  c.ClassId, c.ClassName, m.ProductId, m.ProductName

from ProductClass c

 inner join Products m on c.ClassId = m.ClassId