what flights fly from denver to san francisco on monday tuesday wednesday thursday and friday 
return flights ;return #1 which  fly from  denver ;return #2 to san francisco ;return #3 on  monday ;return #3 on  tuesday ;return #3 on  wednesday ;return #3 on  thursday ;return #3 on  friday ;return #4 , #5 ,  #6 ,   #7 and  #8
['select', 'filter', 'filter', 'filter', 'filter', 'filter', 'filter', 'filter', 'union']