本文通过例子演示了Oracle分析函数 —— rank, dense_rank, row_number的用法。

//首先建score表
create table score(
course   nvarchar2(20),
stu_name nvarchar2(20),
score   number(2));

//插入数据
insert into score values ('Math','Tough1',95);
insert into score values ('Math','Tough2',93);
insert into score values ('Math','Tough3',94);
insert into score values ('Math','Tough4',95);
insert into score values ('Math','Tough5',94);

//查看
select * from score order by score desc;

COURSE	STU_NAME	SCORE
Math	Tough1	95
Math	Tough4	95
Math	Tough5	94
Math	Tough3	94
Math	Tough2	93

• rank() over

按course分组，并按score排名。
若score相同，rank会跳跃式排名——例如有两个第一名，接下来直接是第三名，没有第二名。

select course, stu_name, score,
       rank() over(partition by course order by score desc) "RANK"
from   score;

COURSE	STU_NAME	SCORE	RANK
Math	Tough1	95	1
Math	Tough4	95	1
Math	Tough5	94	3
Math	Tough3	94	3
Math	Tough2	93	5

• dense_rank() over

按course分组，并按score排名。
若score相同，dense_rank不会跳跃式排名——例如有两个第一名，接下来是第二名。

select course, stu_name, score,
      dense_rank() over(partition by course order by score desc) "RANK"
from score;

COURSE	STU_NAME	SCORE	RANK
Math	Tough1	95	1
Math	Tough4	95	1
Math	Tough5	94	2
Math	Tough3	94	2
Math	Tough2	93	3

• row_number() over

按course分组，并按score排名。
若score相同，row_number排名也不一样。

select course, stu_name, score,
      row_number() over(partition by course order by score desc) "RANK"
from score;

COURSE	STU_NAME	SCORE	RANK
Math	Tough1	95	1
Math	Tough4	95	2
Math	Tough5	94	3
Math	Tough3	94	4
Math	Tough2	93	5

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