5、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩

5、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩

SELECT st.s_id,st.s_name,c,s FROM student st LEFT JOIN (SELECT sc.s_id,COUNT(sc.c_id) c,SUM(sc.s_score) s FROM score sc GROUP BY sc.s_id) d ON st.s_id=d.s_id