按课程号分类，统计相应的选课人数（）
A: select cid, count(distinct sid) from sc group by cid
B: select cid, count(*) from student group by cid
C: select cid, count(distinct cid) from sc group by cid
D: select cid, count(distinct sid) from student group by cid
A: select cid, count(distinct sid) from sc group by cid
B: select cid, count(*) from student group by cid
C: select cid, count(distinct cid) from sc group by cid
D: select cid, count(distinct sid) from student group by cid
举一反三
- 统计选修了a001课程的学生的平均成绩( ) A: select cid,avg(grade) from student group by cid having cid=’a001’ B: select cid,avg(grade) from student where cid=’a001’ group by cid C: select cid,avg(grade) from course where cid=’a001’ group by cid D: select cid,avg(grade) from sc where cid=’a001’ group by cid
- 查询选修了a001号课程的学生的最高成绩（） A: select cid, max(grade) from course where cid=’a001’ group by cid B: select cid,max(grade) from student where cid=’a001’ group by cid C: select cid, max(grade) from sc where cid=’a001’ group by cid D: select cid, max(grade) from student group by cid having cid=’a001’
- 按照学号进行分组，统计学生的平均成绩（） A: select sid, avg(grade) from student group by cid B: select sid, avg(grade) from student group by sid C: select sid, avg(grade) from sc group by sid D: select sid, avg(grade) from sc group by cid
- 按照课程号进行分组，统计学生平均成绩大于60分的学生的信息( ) A: select cid,avg(grade) from sc group by cid having avg(grade)>60 B: select cid,avg(grade) from student group by cid having avg(grade)>60 C: select cid,avg(grade) from course where avg(grade)>60 group by cid D: select cid,avg(grade) from student where avg(grade)>60 group by cid
- 查询选修了2门课程以上的学生学号（） A: select sid,count(*) from sc group by sid having count(*)>=2 B: select sid,count(*) from sc group by sid where count(*)>=2 C: select sid,count(*) from sc where count(*)>=2 group by sid D: select sid,count(*) from sc group by cid having count(*)>=2