下列是各表的詳情，不想自己建表的同學可以直接copy code，資料隨意。
建立表成績詳情表：
CREATE TABLE score (
id int(10) NOT NULL AUTO_INCREMENT,
subject_id int(10) DEFAULT NULL,
student_id int(10) DEFAULT NULL,
score float DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB AUTO_INCREMENT=19 DEFAULT CHARSET=utf8;

建立學生表：
CREATE TABLE student

(
id int(10) NOT NULL AUTO_INCREMENT,
name varchar(10) DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8;

建立科目表：
CREATE TABLE subject (
id int(10) NOT NULL AUTO_INCREMENT,
name varchar(10) DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

查詢語句：

select a.id,a.subject_id,a.student_id,a.score from score as a left join score as b on a.subject_id=b.subject_id and a.score>=b.score
group by a.subject_id,a.student_id,a.score
having count(a.subject_id)>=4
order by a.subject_id,a.score desc;

分析：先將查詢語句分別拆開來一步一步分析
select a.id,a.subject_id,a.student_id,a.score,b.id,b.subject_id,b.student_id,b.score from score as a left join score as b on a.subject_id=b.subject_id; #這裡把所有的列都列出來了便於對比
這裡把表score的每一條同subject_id的資料都連線起來，如圖所示：共18*6=108條資料

現在我們可以再進一步處理上面的資料了。這裡我們再加上 a.score<=b.score 這個條件篩選再進行一次篩選。
select a.id,a.subject_id,a.student_id,a.score,b.id,b.subject_id,b.student_id,b.score from score as a left join score as b on a.subject_id=b.subject_id and a.score<=b.score;
有同學可能會問為什麼不用a.score<b.score來篩選。如果用a.score<b.score來進行篩選的話，如果資料中某個科目出現大量的並列第一名的話那麼第一名就會被過濾掉，以至於得不到結果。如圖：

接下來就是分組：group by a.subject_id,a.student_id,a.score #按subject_id,student_id,score來進行分組；
select a.id,a.subject_id,a.student_id,a.score,b.id,b.subject_id,b.student_id,b.score,count(a.subject_id) from score as a left join score as b on a.subject_id=b.subject_id and a.score>=b.score
group by a.subject_id,a.student_id,a.score; #新增count(a.subject_id)來進行對比易於理解

分組後再進行條件查詢：having count(a.subject_id)>=4；
接下來就是排序：order by a.subject_id,a.score desc。