mysql中的排名函数rank()、dense_rank()、row_number()

1. rank()
   按照某字段的排序结果添加排名，但它是跳跃的、间断的排名，例如两个并列第一名后，下一个是第三名。

SELECT Score,rank() over(ORDER BY Score desc) as 'Rank' FROM score;
# 分组排序
SELECT Score,rank() over([partition by xxx] ORDER BY Score desc) as 'Rank' FROM score;

2. row_number()
   它是将某字段按照顺序依次添加行号。

SELECT Score,row_number() over(ORDER BY Score desc) as 'Rank' FROM score；
# 分组排序
SELECT Score,row_number() over([partition by xxx] ORDER BY Score desc) as 'Rank' FROM score；

3. dense_rank()
   dense 英语中指“稠密的、密集的”。dense_rank()是的排序数字是连续的、不间断。当有相同的分数时，它们的排名结果是并列的，例如，1,2,2,3。

SELECT Score,dense_rank() over(ORDER BY Score desc) as 'Rank' FROM score；
# 分组排序
SELECT Score,dense_rank() over([partition by xxx] ORDER BY Score desc) as 'Rank' FROM score；

4.总结

对比分析rank(), dense_rank(), row_number()

5. 案例

create table score(
Id INT NOT NULL PRIMARY KEY auto_increment,
Score decimal(5,2) NOT NULL
);

insert score(Score)
values(88),
(56),
(77),
(88),
(75),
(77),
(56),
(33);

select * from score;

select Id, Score, DENSE_RANK() OVER(ORDER BY Score DESC) AS `Rank`
from score;

dense_rank()应用示例