实验答案(四-五-六)参考答案.doc

实验四 简单查询和连接查询
1. 简单查询实验
用Transact-SQL语句表示下列操作，在“学生选课“数据库中实现其数据查询操作：
(1) 查询数学系学生的学号和姓名。
select sno,sname
from student
where dept='数学系';
(2) 查询选修了课程的学生学号。
select distinct(sno)
from sc;
(3) 查询选修课程号为0101的学生学号和成绩，并要求对查询结果按成绩降序排列，如果成绩相同则按学号升序排列。
select distinct(sno),grade
from sc
where cno='0101'
order by grade desc,sno asc;
(4) 查询选修课程号为0101的成绩在80-90 分之间的学生学号和成绩，并将成绩乘以系数0.8 输出。
select distinct(sno),grade*0.8 as 'sore'
from sc
where cno='0101' and grade between 80 and 90;
(5) 查询数学系或计算机系姓张的学生的信息。
select *
from student
where dept in ('数学系','计算机系')and sname like '张%' ;
(6) 查询缺少了成绩的学生的学号和课程号。
select sno,cno
from sc
where grade is null;
2. 连接查询实验
用Transact-SQL语句表示，并在“学生选课”数据库中实现下列数据连接查询操作：
(1) 查询每个学生的情况以及他（她）所选修的课程。
select student.*,ame
from student,sc,course
where student.sno=sc.sno and o=o;
(2) 查询学生的学号、姓名、选修的课程名及成绩。
select student.sno,sname,cname,grade
from student,sc,course
where student.sno=sc.sno and o=o;
(3) 查询选修离散数学 课程且成绩为90 分以上的学生学号、姓名及成绩。
select student.sno,sname,grade
from student,sc,course
where student.sno=sc.sno and o=o
and cname='离散数学' and grade>=90;
(4) 查询每一门课的间接先行课（即先行课的先行课）。
select o,second.pcno
from course as first,course as second
where first.pcno=o;
实验五 嵌套查询
用TransacTransact-SQL语句表示，在学生选课库中实现其数据嵌套查询操作：
(l) 查询选修了离散数学的学生学号和姓名。
select sno,sname
from student
where sno in
(select sno
from sc
where cno=
(select cno
from course
where cname='离散数学'));
(2) 查询0101课程的成绩高于张林的学生学号和成绩。
select sno,grade
from sc
where cno='0101' and grade>
(select grade
from sc
where cno='0101' and sno=(select sno
From student
Where sname='张林'));
(3) 查询其他系中年龄小于计算机系年龄最大者的学生。
select *
from student
where dept<>'计算机系' and age<(select max(age)
from student
where dept='计算机系');
(4) 查询其他系中比计算机系学生年龄都小的学生。
(3)中的max换成min即可。
(5) 查询同牟万里数据库原理课程分数相同的学生的学号。

select sno
from sc
where grade=(select grade
from student,sc,course
where student.sno=sc.sno and o=o and ame='数据库原理' and sname='牟万里');
(6) 查询选修了0206 课程的学生姓名。
select sname
from student
where sno in (select sno
from sc
where cno='0206');
(7) 查询没有选修0206 课程的学生姓名。
在(5)的in前加not即可。
(8) 查询选修了全部课程的学生的姓名。
SELECT SNAME
FROM STUDENT
WHERE SNO IN (
SELECT SNO
FROM SC
GROUP BY SNO
HAVING COUNT(*)=
( SELECT COUNT(*)
FROM COURSE));

select sname
from student
where not exists (select *
from course
where not exists (select *
from sc
where sno=student.sno and cno=o));
(9) 查询与学号为“09001103”的学生所选修的全部课程相同的学生学号和姓名。
select sno,sname
From student
Where sno<>'09001103' and not exists(
select *
From sc as x
Where sno='09001103' and not exists
(select *
From sc as y
Where y.sno=student.sno and o=o )) ; (10) 查询至少选修了学号为“09001103”的学生所选修的全部课程的学生学号和姓名。
select sno,sname
from student
where sno in(select scx.sno
from sc scx
where not exists(select *
from sc scy
where scy.sno='09001103' and not exists(select *
from sc scz
where scz.sno=scx.sno and o=o)));
实验六 组合查询和统计查询
在学生选课数据库中实现其查询操作：
(1) 查找选修“计算机基础”课程的学生成绩比此课程的平均成绩大的学生学号，成绩。
select x.sno,x.grade
From sc as x
Where x.grade>(
select avg(y.grade)
From sc as y,course as c
Where ame='计算机基础') and o=
(select cno
From course
Where cname='计算机基础');
(2) 查询选修计算机基础课程的学生的平均成绩。
select avg(grade)
From sc
Where sno in
(select sno
From sc
Where cno=
(select cno
From course
Where cname='计算机基础'));
(3) 查询年龄大于女同学平均年龄的男同学姓名和年龄。

select sname,age
From student
Where sex='男' and age>
(select avg(age)
From student
Where sex='女');
(4) 列出各系学生的总人数，并按人数进行降序排列。
select dept ,count(*) as total
From student
Group by dept
order by total desc;
(5) 统计各系各门课程的平均成绩。
select dept ,cno,avg(grade)
From student,sc
Group by dept,cno
(6) 查询选修计算机基础和离散数学的学生学号和平均成绩。
select s1.sno,avg(grade) as 平均分
From sc as s1
Where '计算机基础' in
(select cname
From course
Where cno in
(select o
From sc as s2
Where s2.sno=s1.sno)) and '离散数学' in
(select cname
From course
Where cno in
(select cno
From sc as s3
Where s3.sno=s1.sno))
Group by s1.sno;