近日系统要实现总分成绩排名，而且相同分数的学生排名要一样，在网上搜了一圈，没有找到合适的方法，只能靠自己实现了，这里提供两种方法

1、sql查询实现

测试如下：

mysql> select * from score ;

+----------+--------------+---------------------+--------------+-------+

| study_no | student_name | subject_id | subject_name | score |

+----------+--------------+---------------------+--------------+-------+

| student1 | student1 | CodeCourseSubject_0 | 语文 | 120 |

| student2 | student2 | CodeCourseSubject_0 | 语文 | 110 |

| student3 | student3 | CodeCourseSubject_0 | 语文 | 110 |

| student4 | student4 | CodeCourseSubject_0 | 语文 | 80 |

| student5 | student5 | CodeCourseSubject_0 | 语文 | 81 |

| student1 | student1 | CodeCourseSubject_2 | 英语 | 150 |

| student2 | student2 | CodeCourseSubject_2 | 英语 | 130 |

| student3 | student3 | CodeCourseSubject_2 | 英语 | 130 |

| student4 | student4 | CodeCourseSubject_2 | 英语 | 44 |

| student5 | student5 | CodeCourseSubject_2 | 英语 | 45 |

+----------+--------------+---------------------+--------------+-------+

10 rows in set

首先这里对科目显示进行了行列转换，并且对以学号study_no进行分组计算总分，并且按排名排序，

sql如下：

SELECT @rownum:=@rownum+1 AS rownum,

if(@total=total,@rank,@rank:=@rownum)as rank,

@total:=total,

A.*

FROM　(SELECT study_no AS studyNo,

student_name AS studentName,

SUM(score) AS total,

SUM(IF(subject_id='CodeCourseSubject_0',score,0)) AS 语文,

SUM(IF(subject_id='CodeCourseSubject_2',score,0)) AS 英语

FROM score GROUP BY study_no ORDER BY total DESC

)A,(SELECT @rank:=0,@rownum:=0,@total:=null)B

结果：

+--------+------+---------------+----------+-------------+-------+-------+-------+

| rownum | rank | @total:=total | studyNo | studentName | total | 语文 | 英语 |

+--------+------+---------------+----------+-------------+-------+-------+-------+

| 1 | 1 | 270.0 | student1 | student1 | 270.0 | 120.0 | 150.0 |

| 2 | 2 | 240.0 | student2 | student2 | 240.0 | 110.0 | 130.0 |

| 3 | 2 | 240.0 | student3 | student3 | 240.0 | 110.0 | 130.0 |

| 4 | 4 | 126.0 | student5 | student5 | 126.0 | 81.0 | 45.0 |

| 5 | 5 | 124.0 | student4 | student4 | 124.0 | 80.0 | 44.0 |

+--------+------+---------------+----------+-------------+-------+-------+-------+

5 rows in set

可见排名第二名有两个相同的分数，后面的排名自动往后移。

下面提供另外一种在程序中实现的方法：

2、程序实现

首先获得全班总分并且以降序排序

public List findAllTotalScore() {

String sql = "SELECT study_no,sum(score) AS total from score s ";

javax.persistence.Query query = em.createNativeQuery(sql);

return query.getResultList();

}

对获得的总分信息进行排序和封装成map(study_no，rank)

private Map rank(List objects) {

long previousRank = 1;

double total = 0;

//记录排名的map，map

Map rankMap = new HashMap<>();

for (int i = 0; i < objects.size(); i++) {

Object[] object = objects.get(i);

//计算名次，相同分数排名一样

if (total == (double) object[1]) {

rankMap.put(object[0].toString(), previousRank);

} else {

rankMap.put(object[0].toString(), i + 1L);

total = (double) object[1];

previousRank = i + 1;

}

}

return rankMap;

}

使用map直接根据学号就可以获得成绩排名。