建表语句点击详见
– 以如下形式显示：课程ID，课程name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率 – 及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90
SELECT c.c_id, c.c_name, MAX(sc.s_score) "最高分", MIN(sc.s_score) "最低分", AVG(sc.s_score) "平均分" , ((SELECT COUNT(s_id) FROM score WHERE s_score>=60 AND c_id=c.c_id )/(SELECT COUNT(s_id) FROM score WHERE c_id=c.c_id)) "及格率", ((SELECT COUNT(s_id) FROM score WHERE s_score>=70 AND s_score<80 AND c_id=c.c_id )/(SELECT COUNT(s_id) FROM score WHERE c_id=c.c_id)) "中等率", ((SELECT COUNT(s_id) FROM score WHERE s_score>=80 AND s_score<90 AND c_id=c.c_id )/(SELECT COUNT(s_id) FROM score WHERE c_id=c.c_id)) "优良率", ((SELECT COUNT(s_id) FROM score WHERE s_score>=90 AND c_id=c.c_id )/(SELECT COUNT(s_id) FROM score WHERE c_id=c.c_id)) "优秀率" FROM course c LEFT JOIN score sc ON sc.c_id=c.c_id GROUP BY c.c_id