give me the flights from new york city to las vegas on sunday and the flights from memphis to las vegas on sunday 
return flights ;return #1 from  new york city ;return #2 to las  vegas ;return #3 on  sunday ;return #1 from  memphis ;return #5 to las  vegas ;return #6 on  sunday ;return #4 , #7
['select', 'filter', 'filter', 'filter', 'filter', 'filter', 'filter', 'union']