-- 3、查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩

SELECT st.s_id, st.s_name, ROUND (AVG(sc.s_score),2) FROM student st LEFT JOIN score sc ON st.s_id=sc.s_id GROUP BY st.s_id HAVING AVG(sc.s_score)>=60;