三个基本表：学生表(Student)、课程表（Course）、学生选课表（SC）
SQL数据库操作语句习题
三个基本表：学生表(Student)、课程表（Course）、学生选课表（SC）
这是我课本上习题作业，没有参考答案，是我自己写的。语句可能有错误！！！
有误请指正，谢谢。
《数据库原理与应用教程》第4版 何玉洁 编著 机械工业出版社
下面两个地址数据库内容一样 百度网盘里有txt的数据
配套数据库sql server（主要是想赚积分）https://download.csdn.net/download/jivder/11162509
百度网盘链接(有txt数据文件): 链接：https://pan.baidu.com/s/14HiZPpX1lSljrTgmjQLinw
提取码：q72d
表结构
CREATE TABLE [dbo].[Course](
[Cno] [nchar](4) NOT NULL,
[Cname] [varchar](50) NOT NULL,
[Credit] [tinyint] NULL,
[Semester] [tinyint] NULL
) ON [PRIMARY]
CREATE TABLE [dbo].[SC](
[Sno] [nchar](7) NOT NULL,
[Cno] [nchar](4) NOT NULL,
[Grade] [tinyint] NULL
) ON [PRIMARY]
CREATE TABLE [dbo].[Student](
[Sno] [nchar](7) NOT NULL,
[Sname] [nchar](10) NOT NULL,
[Sex] [nchar](2) NULL,
[Sage] [tinyint] NULL,
[Sdept] [nchar](20) NULL
) ON [PRIMARY]
问题
- 查询学生选课表中的全部数据
SELECT * FROM SC
- 查询计算机系学生的姓名、年龄
SELECT Sname, Sage FROM Student WHERE Sdept = '计算机系'
- 查询成绩在70-80分之间的学生的学号、课程号和成绩
select Sno, Cno, Grade from SC
where Grade between 70 and 80
- 查询计算机系年龄在18-20之间且性别为“男”的学生的姓名、年龄。
select Sname, Sage from Student
where Sage between 18 and 20 and Ssex = '男'
and Sdept = '计算机系'
- 查询课程号为“c001”的课程的最高分数。
select top 1 Grade from SC
where Cno = 'c001'
- 查询计算机系学生的最大年龄和最小年龄。
select MAX(Sage) as 最大年龄, MIN(Sage) as 最小年龄 from Student
- 统计每个系的学生人数
select Sdept as 系别, COUNT(Sno) as 学生人数 from Student
group by Sdept
- 统计每门课程的选课人数和考试最高分
select Cno as 课程号, COUNT(Sno) as 选课人数, MAX(Grade) as 最高分
from SC
group by Cno
- 统计每个学生的选课门数和考试总成绩，并按选课门数升序显示结果。
select Student.Sno 学号, Student.Sname 姓名, count(Grade) 门数, sum(Grade) 总成绩 from SC
join Student on Student.Sno = SC.Sno
group by SC.Sno, Student.Sname, Student.Sno
order by count(Grade)
- 查询总成绩超过200分的学生，要求列出学号、总成绩。
select Student.Sno 学号,sum(Grade) 总成绩 from SC
join Student on Student.Sno = SC.Sno
group by SC.Sno, Student.Sname, Student.Sno
having sum(Grade) > 200
- 查询选修了“c002”号课程的学生的姓名和所在系。
select Sname, Sdept from Student S
join SC on S.Sno = SC.Sno
where Cno = 'c002'
- 查询成绩80分以上的学生的姓名、课程号和成绩，并按成绩降序排列结果。
select Student.Sname, Cno, Grade from Student
join SC on Student.Sno = SC.Sno
where Grade > 80
order by Grade desc
- 查询那些学生没有选课，要求列出学号、姓名、所在系。
select sno, Sname, Sdept from Student left join SC on student.sno= sc.sno
where sc.sno is null
- 查询与Java在同一学期开设课程的课程名和开课学期。
select Cname, Semester from Course
where Semester = (
select Semester from Course where Cname='Java')
- 查询与李勇年龄相同的学生的姓名、所在系和年龄。
select Sname 姓名, Sdept 所在系, Sage 年龄 from Student
where Sage = (select Sage from Student where Sname = '李勇')
- 用子查询实现如下查询。
(1)查询选修了“c001”号课程的学生的姓名和所在系。
select Sname, Sdept from Student
where Sno in (
select Sno from SC
where Cno = 'c001')
(2)查询数学成绩80分以上的学生的学号、姓名、课程号和成绩。
select student.Sno, sname,Sdept, Cno, Grade from Student
join SC on Student.Sno = SC.Sno
where Sdept = '数学系' and Grade >= 80
(3)查询计算机系考试成绩最高的学生的姓名。
select Sname from Student x join SC on x.Sno = SC.Sno
where Sdept = '计算机系' and Grade = (
select MAX(Grade) from SC join Student y on y.Sno = SC.Sno
where Sdept = '计算机系')
(4)查询数据结构考试成绩最高的学生的姓名、所在系、性别和成绩。
select Sname, Sdept, Ssex, Grade from Student s join SC on s.Sno = SC.Sno
where Grade = (
select MAX(Grade) from SC join Course c on c.Cno = SC.Cno
where Cname = '数据结构')
- 查询没有选修Java课程的学生的姓名和所在系。
select sname,sdept from Student
where sno in (
select sno from sc
where cno in (select cno from Course
where Cname != 'Java'))
- 查询计算机系没有选课的姓名和性别。
select Sname from Student
left join SC on Student.Sno = SC.Sno
where Sdept = '计算机系' and SC.Sno is null
- 创建一个新表，表名为text_t，其结构体为（COL1， COL2， COL3）,其中：
COL1：整型，允许空值
COL2：字符型，长度为10，不允许空值
COL3：字符型，长度为10，允许空值
试写出按行插入如下数据的语句
| COL1 | COL 2 | COL2 |
|---|---|---|
| B1 | ||
| 1 | B2 | C2 |
| 2 | B3 |
insert into test_t(COL2) values ('B1')
insert into test_t(COL1,COL2) values ('1','B1')
insert into test_t(COL1,COL2) values ('2','B3')
- 删除考试成绩低于50分的同学的选课记录。
delete from SC
where Grade < 50
- 删除没有人选的课程记录。
delete from Course
where Cno not in (select Cno from SC)
- 删除计算机系Java成绩不及格学生的Java选课记录
查找60分以下的课程名
select Sno, Cname, Grade from SC
join Course on sc.Cno= Course.Cno
where Grade <60
删除语句
delete from SC
where Grade < 60 and Cno in (
select Cno from Course
where Cname = 'Java')
- 将第2学期开设的所有课程的学分增加2分。
update Course set Credit = Credit + 2
where Semester = '2'
- 将Java课程学分改为3分。
update Course set Credit = 3
where Cname = 'Java'
- 将计算机系学生的年龄增加1岁。
update Student set Sage = Sage + 1
where Sdept = '计算机系'
- 将信息系学生的“计算机文化”课程的考试成绩加5分。
select sname, Sdept, grade from Student s
join SC on s.Sno = sc.Sno
where Sdept= '信息系' and Cno in (
select Cno from Course
where Cname = '计算机文化学')
- 查询每个系年龄大于等于20的学生人数，并将结果保存到一个新永久表Dept_Age中。
select Sdept 系名, COUNT(*) 人数 into Dept_Age
from Student
where Sage > = 20
group by Sdept
- 查询计算机系每个学生的Java考试情况，列出学号、姓名、成绩和成绩情况，其中成绩显示规则为：>=90，好；80-89，较好；70-79，一般；60-69，较差，<60，差。
select student.Sno 学号, Sname 姓名,grade 成绩,
case
when Grade >= 90 then '好'
when Grade between 80 and 89 then '较好'
when Grade between 70 and 79 then '一般'
when Grade between 60 and 69 then '较差'
when Grade < 60 then '差'
end as 考试情况
from Student
join SC on Student.Sno = SC.Sno
where Sdept = '计算机系'and Cno in (
select Cno from Course where Cname='Java')
- 统计每个学生的选课门数（包括没有选课的学生），列出学号、选课门数和选课情况，其中选课情况显示规则为：>=6,多；3-5,一般；1-2，偏少；0，未选课。
select s.sno 学号, count(Sc.Cno) 选课门数,
case
when count(sc.Cno) > 4 then '多'
when count(sc.Cno) between 2 and 4 then '一般'
when count(sc.Cno) between 1 and 2 then '少'
when count(sc.Cno) = 0 then '未选'
end as 选课情况
from student s left join sc on s.sno = sc.sno
group by s.Sno
order by COUNT(sc.cno) desc
- 修改全部课程的学分。1-2学期，学分增加5；3-4学期，学分增加3；5-6学期，学分增加1；其他不变。
update Course set Credit = Credit +
case
when Semester between 1 and 2 then 5
when Semester between 3 and 4 then 3
when Semester between 5 and 6 then 1
else 0
end
- 查询“李勇”“王大力”所选的全部课程，列出课程名、开课学期和学分，不重复出现结果。
select Cname 课程名, Credit 学分, Semester 开课学期
from Student S join SC on S.Sno = sc.Sno
join Course c on c.Cno = sc.Cno
where Sname = '李勇'
intersect
select cname 课程名, credit 学分, Semester 开课学期
from Student s join sc on s.Sno = sc.Sno
join Course c on c.Cno = sc.Cno
where Sname = '王大力'
- 查询在第3学期开设课程中，李勇、王大力没选的课程，列出课程名和学分。
select Cname 课程名, Credit 学分
from Student S join SC on S.Sno = sc.Sno
join Course c on c.Cno = sc.Cno
where Sname = '李勇' and Semester = 3
except
select cname 课程名, credit 学分
from Student s join sc on s.Sno = sc.Sno
join Course c on c.Cno = sc.Cno
where Sname = '王大力' and Semester = 3
- 查询在学分>3分的课程中，李勇、王大力所选的相同课程，列出课程名和学分。
select Cname 课程名, Credit 学分
from Student S join SC on S.Sno = sc.Sno
join Course c on c.Cno = sc.Cno
where Sname = '李勇' and Credit > 3
intersect
select cname 课程名, credit 学分
from Student s join sc on s.Sno = sc.Sno
join Course c on c.Cno = sc.Cno
where Sname = '王大力' and Credit > 3