return me the author in the " University of Michigan " whose papers in Databases area have the most total citations . 
return authors ;return #1 in the   University of Michigan ;return papers of #2 ;return #3 that  are in Databases area ;return citations of #4 ;return the   number of  #5 for each #4 ;return the   sum of #6 for each #2 ;return #2 where #7 is  the   highest
['select', 'filter', 'project', 'filter', 'project', 'group', 'group', 'comparative']