如下几个表所示学生、课程、必修课和选课关系,用SQL语言实现下列操作。 列出各门课的平均成绩、最高成绩、最低成绩和选课人数。正确的SQL语句是_____。
A.SELECT 课号,AVG(成绩),MAX(成绩),MIN(成绩),COUNT(学号) FROM 选课GROUP BY 课号;
B.SELECT 课号,AVG(成绩),MAX(成绩),MIN(成绩),COUNT(学号) FROM 选课ORDER BY 课号;
C.SELECT 课号,AVG(成绩),MAX(成绩),MIN(成绩),COUNT(学号) FROM 选课WHERE 课号;
D.SELECT 课号,AVG(成绩),MAX(成绩),MIN(成绩),COUNT(学号) FROM 选课HAVING 课号;