How many more dwellings were constructed between 1950 and 1969 than 1949?
return dwellings ;return constructed of #1 ;return #1 where #2 is between 1950 and  1969 ;return #1 where #2 is 1949 ;return number of  #3 ;return number of  #4 ;return difference of #5 and  #6
['select', 'project', 'comparative', 'comparative', 'aggregate', 'aggregate', 'arithmetic']