ROW_NUMBER()，不允許並列名次、相同值名次不重復，結果如123456……

將score按ID分組排名：row_number() over(partition by id order by score desc)

將score不分組排名：row_number() over(order by score desc)

select id,area,score,

row_number() over(partition by id order by score desc) 分組id排序,

row_number() over(order by score desc) 不分組排序

from students order by id,area;