-- 23、统计各科成绩各分数段人数:课程编号,课程名称,[100-85],[85-70],[70-60],[0-60]及所占百分比

SELECT c.c_id,c.c_name ,((SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id AN
SELECT c.c_id,c.c_name 
,((SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id AND sc.s_score<=100 AND sc.s_score>80)/(SELECT COUNT