Question

帮做几个SQL选择语句吧。。。在线等

（1）查询没有选修任何一门课的学生的姓名、学号。
（2）查询19~21岁的女生的姓名、年龄、课程号、成绩。
（3）查询比平均成绩低的学生的姓名、课程名、成绩。
（4）查询选修课程号为“T10102”的不及格学生的姓名和成绩。
学生表(student)：sno sname gender（性别） department（系） age
课程表(course)：cno cname credit（学分）
选课表(SC表)：sno cno grade （成绩）

知道在请尽快告诉我吧，急。。。。不知道在别浪费时间！！

Answer 1

1.select sno,Sname from student where sno not in (select sno from sc)

2.select a.sName,a.age,c.cName,c.grade from student a
inner join sc b on a.Sno=b.sno
inner join course c on c.cno=b.cno
where a.age bwtween 19 and 21 and a.gender='女'

3.select a.Sname,c.grade from student a
inner join sc b on a.Sno=b.sno
inner join course c on c.cno=b.cno
inner join
(select sno,cno,avg(grade) avggrade from SC
group by sno,cno
) d on a.sno=d.sno and b.cno=d.cno
where c.Grade<模圆游d.avggrade
--这个要上机旦销验证下，我没数据腔好库

4.select a.Sname,c.grade from student a
inner join sc b on a.Sno=b.sno
inner join course c on c.cno=b.cno
where b.cname='T10102' and c.grade<60

Answer 2

(1) select sno,sname from student a
where not exists(select * from SC b where a.sno=b.sno)
(2) select a.sname,a.age,b.cno,b.grade from student a,SC b
where a.sno=b.sno and a.age between 19 and 21 and a.gender='备吵女'
(3) select a.sname,b.cname,c.grade from student a,course b,SC c,
(select cno,avg(grade) from SC group by cno) d
where a.sno=c.sno and b.cno=c.cno and c.cno=d.cno and
c.grade<汪滚冲d.grade
(4) select a.sname,b.grade from student a,SC b where b.cno='T10102'困歼
and b.grade<60 and a.sno=b.sno

Answer 3

1,select sname,sno from student,SC where student.sno not in (select sno from SC)
2,select sname,age,cno,grade from student,course,SC
where age between 19 and 21 and gender='女'
3,select sname,cname,grade from student,course,SC
where sno=(select sno from SC where grade<avg(grade))
4select sname,grade from student,SC
where cno='T10102'扮孝and grade<6这个答厅稿稿案我没空检验，自己再改改敬颤吧。

Answer 4

数据库发下

Answer 5

为什么要查询19--21 岁女生的姓名呢？难道LZ有不可告人的秘密？？！！