How many years difference is there between the most recent record maximum temperature and record minimum temperature?
return maximum temperature  records ;return minimum temperature  records ;return years of #1 ;return years of #2 ;return the  highest of #3 ;return the  highest of #4 ;return the  difference of #5 and  #6
['select', 'select', 'project', 'project', 'aggregate', 'aggregate', 'arithmetic']