How many more households were there than families in the census of 2000?
return the  census ;return #1 of 2000 ;return households of #2 ;return families of #2 ;return number of  #3 ;return number of  #4 ;return difference of #5 and  #6
['select', 'filter', 'project', 'project', 'aggregate', 'aggregate', 'arithmetic']