Which cities have lower temperature in March than in Dec and have never served as host cities?
return cities ;return the  temperature of  #1 ;return #1 where #2 is  lower in March than in  Dec ;return #1 that  have  served as host cities ;return #1 besides  #4 ;return #3 ,  #5
['select', 'project', 'comparative', 'filter', 'discard', 'union']