What are the names, countries, and ages for every singer in descending order of age?
return singers ;return the  names of  every #1 ;return the  countries of  every #1 ;return the  ages of  every #1 ;return #2 ,  #3 ,   #4 ;return #5 sorted by descending order of  #4
['select', 'project', 'project', 'project', 'union', 'sort']