sql排序之rank,row_number,dense_rank的区别

BrotherWind 2019-07-01

--创建测试表
create table te.sc(id int, name varchar(20),class varchar(20), score int);

--给测试表插入数据
insert into te.sc values (1,'张飞','一年一班',100);
insert into te.sc values (2,'刘备','一年一班',99);
insert into te.sc values (3,'李逵','一年一班',95);
insert into te.sc values (4,'小动','一年一班',97);
insert into te.sc values (5,'小智','一年一班',80);
insert into te.sc values (6,'吕布','一年二班',67);
insert into te.sc values (7,'赵云','一年二班',90);
insert into te.sc values (8,'典韦','一年二班',89);
insert into te.sc values (9,'关羽','一年二班',70);
insert into te.sc values (10,'马超','一年二班',98);
insert into te.sc values (11,'张媛','一年一班',100);

不管在oracle,还是在8.0版的mysql中,在排序的时候都可以用到三个函数:rank,row_number,dense_rank

--列出每个班分数排名前三的学生
    select * from (select id, name, class, score , 
                row_number() over (partition by class order by score desc) as r1,
                rank() over (partition by class order by score desc) as r2 ,
                dense_rank() over (partition by class order by score desc) as r3 from te.sc) B where r1<=3 ;

id     name     class     score     r1   r2   r3
1      张飞    一年一班    100        1    1    1
11     张媛    一年一班    100        2    1    1
2      刘备    一年一班    99         3    3    2
10     马超    一年二班    98         1    1    1
7      赵云    一年二班    90         2    2    2
8      典韦    一年二班    89         3    3    3

这三个函数的区别主要在分数一致的情况下,row_number()不重复排序,rank()重复且跳数字排序,dense_rank()重复且不跳数字排序。

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