練習3--查詢所有同學的學生編號、學生姓名、選課總數、所有課程的總成績

查詢所有同學的學生編號、學生姓名、選課總數、所有課程的總成績

--解法一：

select
    t2.s_id,
    t2.s_name,
    count(t1.c_id) as sun_course,
    sum(t1.s_score) as sum_score
from
    student t2
left join score t1 on
    t1.s_id = t2.s_id
group by
    t1.s_id

 

--參考解法：

select
    a.s_id,
    a.s_name,
    count(b.c_id) as sum_course,
    sum(b.s_score) as sum_score
from
    student a
left join score b on
    a.s_id = b.s_id
group by
    a.s_id,
    a.s_name;

 

--2019/04/17