A
SELECT 学号, AVG(成绩) AS 平均成绩 FROM Student
GROUP BY 学号 HAVING COUNT(课程号)>3
B
SELECT 学号, AVG(成绩) AS 平均成绩 FROM Student
GROUP BY 课程号 HAVING COUNT(课程号)>3
C
SELECT 学号, AVG(成绩) AS 平均成绩 FROM Student
GROUP BY 学号 HAVING COUNT(课程号)>4
D
SELECT 学号, AVG(成绩) AS 平均成绩 FROM Student
GROUP BY 课程号 HAVING COUNT(DISTINCT 学号)>3
