begin
   for c in (select table_name tn from user_tables where table_name <> upper(table_name)) loop
       begin
          execute immediate 'alter table "'||c.tn||'" rename to '||c.tn;
       exception
          when other then
             dbms_output.put_line(c.tn||'已存在');
       end;
   end loop; 
end;