查询各科成绩前K的同学名称，课程，成绩
Table: course
字段信息
course_id int(11)
name varchar(20)
Table: score
字段信息
id int(11)
student_id int(11)
course_id int(11)
score int(11)
Table: student
字段信息
student_id int(11)
name varchar(20)
SELECT student.name 学生, course.name 科目, mscore.score 成绩FROM (SELECT * FROM SCORE OSCORE WHERE (SELECT COUNT(*) FROM SCORE ISCORE WHERE ISCORE.COURSE_ID = OSCORE.COURSE_ID AND ISCORE.SCORE > OSCORE.SCORE) < 3 ORDER BY OSCORE.COURSE_ID,OSCORE.SCORE DESC) mscore, student, courseWHERE student.student_id = mscore.student_id AND course.course_id = mscore.course_id
