return me the author in the " University of Michigan " whose papers in Databases area have the most total citations .
SELECT t1.name FROM DOMAIN AS t4 JOIN domain_publication AS t2 ON t4.did  =  t2.did JOIN publication AS t5 ON t5.pid  =  t2.pid JOIN writes AS t3 ON t3.pid  =  t5.pid JOIN author AS t1 ON t3.aid  =  t1.aid JOIN organization AS t6 ON t6.oid  =  t1.oid WHERE t4.name  =  "Databases" AND t6.name  =  "University of Michigan" GROUP BY t1.name ORDER BY SUM ( t5.citation_num ) DESC LIMIT 1;
SELECT t1.name FROM DOMAIN AS t4 JOIN domain_publication AS t2 ON t4.did  =  t2.did JOIN publication AS t5 ON t5.pid  =  t2.pid JOIN writes AS t3 ON t3.pid  =  t5.pid JOIN author AS t1 ON t3.aid  =  t1.aid JOIN organization AS t6 ON t6.oid  =  t1.oid WHERE t4.name  =  "Databases" AND t6.name  =  "University of Michigan" GROUP BY t1.name ORDER BY SUM ( t5.citation_num ) DESC LIMIT 1;
[{'Nenhum': 'Nenhum resultado encontrado'}]