A.SELECT课程名称,开课院系,COUNT(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.课程编号二学生成绩.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