Show name, country, age for all singers ordered by age from the oldest to the youngest.
return singers ;return names of  #1 ;return countries of  #1 ;return ages of  #1 ;return #2 ,  #3 ,   #4 ;return #5 sorted by #4 from  oldest to youngest
['select', 'project', 'project', 'project', 'union', 'sort']