我相信您正在寻找DENSE_RANK()

with your_table(entity, attribute) as (
  select 'a', 'Car' 
  union all select 'a', 'Car' 
  union all select 'a', 'Bus' 
  union all select 'b', 'Car' 
  union all select 'b', 'Cycle' 
  union all select 'C', 'Car'
  union all select 'D', 'Bus' 
  union all select 'D', 'Motocyle(?)' 
  union all select 'D', 'Car' 
  union all select 'a', 'Cycle' 
  
)
select 
  dense_rank() over (order by entity) as ID, 
  entity, 
  attribute 
from your_table

dbfiddle