Oracle问题——排名函数(rank与dense_rank)

已知：两种排名方式(分区和不分区):使用和不使用partition

两种计算方式(连续,不连续),对应函数：dense_rank,rank

语法：

rank() over (order by 排序字段 顺序)

rank() over (partition by 分组字段
order by 排序字段 顺序)

dense_rank()同上！

例子：

·查询各学生科目为Oracle排名(简单排名)
select sc.s_id,sc.s_name,sub_name,sc.score,
rank() over (order by score desc) 名次
from t_score sc
where sub_name='Oracle'

对比：rank()与dense_rank()：非连续排名与连续排名(都是简单排名)
select sc.s_id,sc.s_name,sub_name,sc.score,
dense_rank() over (order by score
desc) 名次
from t_score sc
where sub_name='Oracle'

查询各学生各科排名(分区排名)
select sc.s_id,sc.s_name,sub_name,sc.score,
rank() over
(partition by sub_name order by score
desc) 名次
from t_score sc

查询各科前2名(分区排名)

根据总分查询各同学名次
select x.*,
rank() over (order by sum_score desc) 名次
from (
select s_id,s_name,sum(score) sum_score
from t_score
group by s_id,s_name ) x