With Contract as 
     (select 1 as id, 'Тверская д.5' as Address from dual
      union all
      select 1 as id, 'Тестовая д.5' as Address from dual
      union all
      select 2 as id, 'Тверская д.5' as Address from dual
      union all
      select 3 as id, 'Бутырская 7' as Address from dual
      union all
      select 2 as id, 'Тестовая д.5' as Address from dual
      union all
      select 1 as id, 'Тестовая д.5' as Address from dual
     )    
     
 
 select ID, Count(*) as Количество_дублей 
   from Contract
   group by (ID)  
   having Count(*)>1
   Order by Количество_дублей Desc