Simple query and connection query of the experimental report database of the course "Database Principles and Applications"

Simple query and connection query of the experimental report database of the course "Database Principles and Applications"

1. The purpose of the experiment

1. Master the syntax of simple query and connection query, proficient in grouping and sorting in data query, as well as external connection and self-connection.
2. Master the usage of SQL Server Management Studio, and be able to modify query statements proficiently according to error warnings.

2. Experimental process and analysis

1. Experimental content
1. Simple query operation. Including selection condition expression, simple expression output, alias application, fuzzy query, data sorting, data grouping, etc.
2. Connect query operation. Including equivalent connection, natural connection, Cartesian product, self-connection, external connection.
2. Experimental process
Experiment one:
build a table and insert data The
table structure in the student elective database is as follows:
students (student number, name, age, gender, department);
courses (course number, course name, credits, prior course);
elective courses ( Student number, course number, grade);
the following data query operation is implemented in the student elective database.

    --创建学生表
create table student
(
  s_num  int PRIMARY KEY,
  s_name varchar(20)not null,
  s_age int check(s_age between 10 and 35),
  s_sex varchar(10) check(s_sex in('男', '女')),
  s_unit varchar(20)
)
drop table student 
select * from student
--插入数据
insert into student values (1815001,'张三',18,'男','数学系'),
                          (1815002,'李白',30,'女','计算机系'),
						  (1815003,'后裔',11,'男','计算机系'),
						  (1815004,'翠花',25,'女','数学系'),
						  (1815005,'狗蛋',21,'男','机械系');
						  
--创建课程表
create table course
(
c_num varchar(20) PRIMARY KEY,
c_name varchar(20) not null,
c_credit  int check(c_credit in (1,2,3,4,5,6)),
front varchar(20) 
)
--插入数据
drop table course
insert into  course values ('C1','C语言',2,' '),
							('C2','程序设计电路',2,'c1'),
							('C3','数字电路',3,'C1'),
							('C4','计算机组成',3,'C3'),
							('C5','计算机网络',4,'C4'),
							('C6','操作系统',3,'C5');

select * from course
--创建选课表
create table selectCourse
(
 s_num  int,
 c_num varchar(20),
 score numeric(3,1)   ,
 primary key (s_num,c_num),
 foreign key ( s_num) references student(s_num),
 foreign key (c_num) references course(c_num),
)
drop table selectCourse
--插入数据

insert into  selectCourse(s_num, c_num, score ) 
                           values(1815001,'C1',70),
                                 (1815001,'C2',80),
								 (1815001,'C3',88),
								 (1815001,'C4',78),
								 (1815001,'C5',88),
								 (1815001,'C6',98),
								 (1815005,'C3',88),
								 (1815002,'C1',80),
								 (1815003,'C1',88),
								 (1815004,'C1',98)
insert into  selectCourse(s_num, c_num ) 
                                 values(1815005,'C1')

数据查询
--1)求数学系学生的学号和姓名
select  s_num as '学号' ,s_name as '姓名' from  student where s_unit='数学系';

--2)求选修了课程的学生学号
select distinct s_num as '学生学号' from selectCourse where  c_num is not null

--3)求选修C1课程的学生学号和成绩,结果按成绩降序排列,如成绩同按学号升序排列
select s_num as '学号'  ,  score as '成绩' from  selectCourse where   c_num ='C1' and score  is not null order by  score

--4)求选修课程C1成绩在80~90之间的学生学号和成绩,并将成绩乘以0.8输出
select s_num as '学号', score*0.8  as '成绩' from  selectCourse  where   c_num ='C1' and ( score between 80 and 90) order by  score

--5)求数学或计算机系姓张的学生的信息
select * from  student where s_name like '张%' and 
                s_num in (select s_num from  student where  s_unit='计算机系' or s_unit ='数学系')

--6)查询每个学生的选课门数，并输出选修5门以上的学生学号。
select   s_num as '学号'    from  selectCourse   group by s_num  having  count(c_num)>5;

--7)求缺少了成绩的学生的学号和课程号
select   s_num as '学号' ,c_num as '课程号'  from  selectCourse where  score is null

--8)查询各个系的学生人数
select  s_unit as '系'  ,count(s_unit) as '人数 ' from student group by s_unit

--9)求学生的学号、姓名、选修的课程名及成绩
select  student.s_num as '学号'  ,student.s_name  as '姓名' ,
        selectCourse.c_num as '课程名',selectCourse.score as '成绩' 
		from  student join  selectCourse  on student.s_num=  selectCourse.s_num 
                                        
--10)求选修课程C1成绩在80~90之间的学生学号、姓名及成绩
select  student.s_num as '学号'  ,student.s_name  as '姓名' ,
        selectCourse.score as 'C1成绩' 
		from  student join  selectCourse  on student.s_num=  selectCourse.s_num 
		where (selectCourse.score between 80 and 90)
                                        
--11)求选修了学分是3的课程的学生学号。
select  student.s_num as '学号' 
      from  selectCourse 
	  join  student   on student.s_num=  selectCourse.s_num
	  join  course on course.c_num=selectCourse.c_num
	  where  course.c_credit=3

--12)查询每一门课的间接先行课（即先行课的先行课）
SELECT  k1.c_num as '课程号',k1.c_name as '课程名',k2.front  '间接先行课'
FROM  Course as k1 ,
 Course as k2
where k1.front= k2.c_num
SELECT  k2.front
FROM   Course k2

Improve experiment:
build table and insert data
(1) Establish employee department database, database involves employee table and department table, and input data into the table.
Employee table
Employee number Name Gender Age Department
1010 Li Yongnan 20 11
1011 LiuChennv19 12
1012 WangMinnu22 12
1014 ZhangLiman21 13

Department Table
Department Number Department Name Telephone
11 Production Section 566
12 Planning Section 578
13 First Workshop 467
14 Research Institute

      --创建职工部门
create table employee
(
  职工号 int PRIMARY KEY,
  姓名 varchar(20)not null,
  性别 varchar(10) check(性别 in('男', '女')),
  年龄 int check(年龄 between 10 and 35), 
  所在部门 varchar(20)
)
select * from employee
--插入相关数据
insert into  employee values(1010,'李勇','男',20,11),
                             (1011,'刘晨','女',19,12),
							 (1012,'王敏','女',22,12),
							 (1014,'张立','男',21,13)

--创建部门表
create table department
(
  部门号 varchar(20),
  部门名称 varchar(20)not null,
  电话 varchar(11) 
)
--插入相关数据
insert  into  department   values(11,'生产科',566)
insert  into  department   values(12,'计划科',578)
insert  into  department   values(13,'一车间',467)
insert  into  department (部门号,部门名称)  values(14,'科研所')
数据查询
--1)查询每个职工的信息，及所对应的部门电话。
select 职工号,姓名,性别,年龄,所在部门,电话 from  employee K1 join  department as k2 on  k1.所在部门=k2.部门号

--2)查询每个部门的名称、电话，及部门职工的姓名、年龄。
select 所在部门,电话,姓名,年龄 from  employee join  department  on  employee.所在部门=department.部门号

--3)针对职工表查询每个部门的职工人数。
select 所在部门 , count(所在部门) as  职工人数  from employee  group by 所在部门
 
--4)查询年龄小于20的职工号、所在部门
select 职工号,所在部门  from  employee where  年龄<20

--5)查询年龄小于20的职工号、所在部门名称
select 职工号,部门名称 from  employee join  department  on  employee.所在部门=department.部门号 where  年龄<20

3. Experimental results

experiment one:

Improve experiment:

4. Experimental analysis

① Analyze the experimental results; the results
obtained through the SQL statement
② explain the problems encountered in the experimental process and how to solve them.
Query the indirect antecedent class of each course (that is, the antecedent class of the antecedent class). I can not query smoothly
resolve
this operation belong to the table to connect with itself, then we need to zd curriculum takes two aliases to distinguish between them.

```sql
SELECT  k1.c_num as '课程号',k1.c_name as '课程名',k2.front  '间接先行课'
FROM  Course as k1 ,
 Course as k2
where k1.front= k2.c_num
SELECT  k2.front
FROM   Course k2