-- 查詢各科成績最高分、最低分和平均分：以以下形式顯示：課程ID，課程name，最高分，最低分，平均分，及格率，中等率，優良率，優秀率 --及格爲>=60，中等爲：70-80，優良爲：80-90，優秀爲：>=90spa
select a.c_id, b.c_name, max(s_score), min(s_score), round(avg(s_score), 2), round(100 *(sum(case when a.s_score >= 60 then 1 else 0 end)/ sum(case when a.s_score then 1 else 0 end)), 2) as 及格率, round(100 *(sum(case when a.s_score >= 70 and a.s_score <= 80 then 1 else 0 end)/ sum(case when a.s_score then 1 else 0 end)), 2) as 中等率, round(100 *(sum(case when a.s_score >= 80 and a.s_score <= 90 then 1 else 0 end)/ sum(case when a.s_score then 1 else 0 end)), 2) as 優良率, round(100 *(sum(case when a.s_score >= 90 then 1 else 0 end)/ sum(case when a.s_score then 1 else 0 end)), 2) as 優秀率 from score a left join course b on a.c_id = b.c_id group by a.c_id, b.c_name
--2019/05/04code