有如下两个关系模式：student（学号，姓名，奖学金)score（学号，课程号，成绩)，则（)是score相对与stu

A.学号

B.学号和课程号

C.学号和成绩

D.课程号

A.课程号，成绩

B.课程号，教工号

C.学号，成绩

D.学号，教工号

A.学号，课程名，成绩

B.学号，课程名

C.学号，成绩

D.学号

A.A.select student_id,student_name,sum(score) from student where score＜60 order by score;

B.B.select distinct student_id,avg(score) from student where score＜60 order by avg(score);

C.C.select student_id,student_name,avg(score) av from student where score＜60 group by student_id order by av asc;

D.D.select student_id,student_name,avg(score) av from student group by student_id where score＜60 order by av asc;

A.查找Score表中平均成绩在85分以上的学生的学号和平均成绩

B.查找平均成绩在85分以上的学生

C.查找Score表中各科成绩在85分以上的学生

D.查找Score表中各科成绩在85分以上的学生的学号和平均成绩

A.学号

B.课程号

C.成绩

D.学号+课程号

现有学生表,课程表和成绩表，三表中的字段如下：

student表:id,student_name

course表：id,course_name

score表:student_id,course_id,score

前提：每个学生都会参加多门课程的考试，每门课程的成绩在score表中都是一条数据

现若要查询出 平均分在60分以上的学生id和学生姓名以及平均分，以下哪个sql语句是正确的？ ()

A.select student_id,student_name,avg(score) av from student s join score sc on s.id=sc.student_id;

B.select student_id,student_name,avg(score) av from student s join score sc on s.id=sc.student_id where av＞60;

C.select student_id,student_name,avg(score) av from student s join score sc on s.id=sc.student_id where av＞60 group by student_id;

D.select student_id,student_name,avg(score) av from student s join score sc on s.id=sc.student_id group by student_id having av＞60;

A.selectavg(nvl(socre,0))fromscoregroupbystuid

B.selectstu_id,avg(sorce)fromscore

C.selectstu_id,avg(score)fromscore

D.selectstu_id,sum(score)/count(score)fromscore

A.A.select * from student where score＞60 and score＜80;

B.B.select * from student where score between 80 and 60;

C.C.select * from student where score＞= 60 or score＜=80;

D.D.select * from student where score＞= 60 and score＜=80;

A.A.主关键字

B.B.主属性

C.C.非主属性

D.D.外关键字