List the top 10 customers by total gross sales. List customers' first and last name and total gross sales.
return customers ;return gross  sales  of #1 ;return sum of #2 for each #1 ;return the  10 highest #3 ;return #1 where #2 is  in #4 ;return first names of #5 ;return last names of #5 ;return gross  sales  of #5 ;return the  sum of #8 for each #5 ;return #6 ,  #7 ,   #9
['select', 'project', 'group', 'aggregate', 'comparative', 'project', 'project', 'project', 'group', 'union']