建表语句点击详见
– 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
,
COUNT(sc
.c_id
),
CASE WHEN SUM(sc
.s_score
) IS NULL THEN 0.00 ELSE ROUND(SUM(sc
.s_score
),2) END AS '总成绩'
FROM student st
LEFT JOIN score sc
ON sc
.s_id
=st
.s_id
GROUP BY st
.s_id
