What are the top 10 customers' first and last names with the highest gross sales, and also what are the sales?
return customers ;return gross sales  of #1 ;return the   10 highest of #2 ;return #1 where #2 is  any  of #3 ;return the   first names of #4 ;return the   last names of #4 ;return the   gross sales  of #4 ;return #5 ,  #6 ,   #7
['select', 'project', 'aggregate', 'comparative', 'project', 'project', 'project', 'union']