SELECT student_id,course_id,number FROM score s1 WHERE
(
SELECT COUNT(1) FROM score s2 WHERE
s1.course_id=s2.course_id AND s2.number>=s1.number
)<=2
ORDER BY course_id,number DESC;
成绩表score
SELECT student_id,course_id,number FROM score s1 WHERE
(
SELECT COUNT(1) FROM score s2 WHERE
s1.course_id=s2.course_id AND s2.number>=s1.number
)<=2
ORDER BY course_id,number DESC;
成绩表score