A.SELECT课程名称,开课院系,COLINT(课程编号)AS选修人数; FROM 学生成绩,课程 WHERE 课程.课程编号=学生成绩,课程编号; GROUP BY 学生成绩.课程编号 HAVING COUNT(*)<=2; ORDER BY COUNT(课程编号) B.SELECT 课程名称,开课院系,COUNT (学号)选修人数; FROM 学生成绩,课程 WHERE 课程.课程编号=学生成绩.课程编号; GROUP BY 学生成绩.学号 HAVING COUNT(*)<=2; ORDER BY COUNT(学号) C.SELECT 课程名称,开课院系,COUNT(学号)AS选修人数; FROM学生成绩,课程 WHERE 课程.课程编号=学生成绩.课程编号; GROUP BY 课程名称 HAVING COUNT(学号)<=2; ORDER BY选修人数 D.SELECT 课程名称,开课院系,COUNT(学号) AS 选修人数; FROM 学生成绩,课程 HAVING COUNT(课程编号)<=2; GROUP BY 课程名称 ORDER BY 选修人数