数据库表--增删改查的操作实例

Posted 2020-10-24 樊琇鸿

一、设置数据库

包括四个表：学生表（Student）、课程表（Course）、成绩表（Score）以及教师信息表（Teacher）。四个表的结构分别如表1-1的表（一）~表（四）所示，数据如表1-2的表（一）~表（四）所示。用SQL语句创建四个表并完成相关题目。

# 创建数据库
create database if not exists z_stu;

#创建学生表（Student）
/*
属性名    数据类型    可否为空    含 义
Sno        varchar (20)    否            学号（主码）
Sname    varchar (20)    否        学生姓名
Ssex        varchar (20)    否        学生性别
Sbirthday    Datetime        可        学生出生年月
 Class    varchar (20)    可        学生所在班级
*/
create  table  if not exists student(
    sno varchar(20) not null comment"学号",
    sname varchar(20) not null comment"学生姓名",
    ssex varchar(20) not null comment"性别",
    sbirthday    datetime comment"生日",
    class varchar(20) comment"班级",
    primary key(sno)
)charset = utf8;

#创建课程表（Course）
/*
属性名    数据类型    可否为空    含 义
Cno        varchar (20)        否        课程号（主码）
Cname    varchar (20)        否        课程名称
Tno        varchar (20)        否        教工编号（外码）
*/
create  table  if not exists course(
    cno varchar(20) not null comment"课程号",
    cname varchar(20) not null comment"课程名称",
    tno varchar(20) not null comment"老师编号",
    primary key(cno)    
)charset utf8;

#创建成绩表（Score）

/*
属性名    数据类型    可否为空    含 义
Sno        varchar (20)        否        学号（外码）
Cno        varchar (20)        否        课程号（外码）
Degree    Decimal(4,1)        可        成绩
                        
主码：Sno+ Cno
*/
create table  if not exists score(
    sno varchar(20) not null comment"学号",
    cno varchar(20) not null comment"课程号",
    degree decimal(4,1),
    primary key(sno,cno)
)charset utf8;

#创建老师表（Teacher）
/*
属性名        数据类型    可否为空    含 义
Tno            varchar (20)        否        教工编号（主码）
Tname        varchar (20)        否        教工姓名
Tsex            varchar (20)            否        教工性别
Tbirthday        datetime            可        教工出生年月
Prof            varchar (20)            可        职称
Depart        varchar (20)        否        教工所在部门
*/
create table if not exists teacher(
    tno varchar(20) not null comment"教工编号",
    tname varchar(20) not null comment"教师姓名",
    tsex varchar(20) not null comment"性别",
    tbirthday datetime comment"生日",
    prof varchar(20) comment"职称",
    depart varchar(20) not null comment"教工所在部门",
    primary key(tno)
)charset utf8;

 

　　开始给表添加数据（增）

学生表（Student）

insert into student values
("108","曾华","男","1977-09-01","95033"),
("105","匡明","男","1975-10-02","95031"),
("107","王丽","女","1976-01-23","95033"),
("101","李军","男","1976-02-20","95033"),
("109","王芳","女","1975-02-10","95031"),
("103","陆君","男","1974-06-03","95031");

 

　课程表（Course）

insert into course values
("3-105","计算机导论","825"),
("3-245","操作系统","804"),
("6-166","数字电路","856"),
("9-888","高等数学","831");

 

　成绩表（Score）

insert into score values
("103","3-245","86"),
("105","3-245","75"),
("109","3-245","68"),
("103","3-105","92"),
("105","3-105","88"),
("109","3-105","76"),
("101","3-105","64"),
("107","3-105","91"),
("108","3-105","78"),
("101","6-166","85"),
("107","6-166","79"),
("108","6-166","81");

 

　教师表（Teacher）　

insert into teacher values
("804","李诚","男","1958-12-02","副教授","计算机系"),
("856","张旭","男","1969-03-12","讲师","电子工程系"),
("825","王萍","女","1972-05-05","助教","计算机系 "),
("831","刘冰","女","1977-08-14","助教","电子工程系");

 

 修改数据（改）：

把姓名为“李军”的性别改为“女”

update student set ssex="女" where sname="李军";

查看表（查）：

select * from student;
select * from course;
select * from score;
select * from teacher;

删除数据（删，以行为单位）：

delete from student where sno in(101,103);

　查看数据所有的实例：　

#1、 查询Student表中的所有记录的Sname、Ssex和Class列。
select sname,ssex,class from student;
#2、 查询教师所有的单位即不重复的Depart列。
 select distinct depart from teacher; 
#3、 查询Student表的所有记录。
select * from student;
#4、 查询Score表中成绩在60到80之间的所有记录。
select * from score where degree  between 60 and 80;
#5、 查询Score表中成绩为85，86或88的记录。
select * from score where degree in(85,86,88);
#6、 查询Student表中“95031”班或性别为“女”的同学记录。
select * from student where class = "95031" or ssex = "女";
 #以Class降序查询Student表的所有记录。
select * from student order by class desc;
# 以Cno升序、Degree降序查询Score表的所有记录。
select * from score order by cno,degree desc;
 #查询“95031”班的学生人数。
select count(*) from student group by class having class="95033";
#10、 查询Score表中的最高分的学生学号和课程号。（子查询或者排序）
select max(degree) from score;
select sno,cno from score where degree=(select max(degree) from score);
# 查询每门课的平均成绩。
select cno,avg(degree) from score group by cno;
#12、查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。
select avg(degree) from score group by cno having cno like"3%" and count(*)>=5 ;
#查询分数大于70，小于90的Sno列。
select sno from score where degree between 70 and 90;
#查询所有学生的Sname、Cno和Degree列。
select student.sname,score.cno,score.degree from student
join score on student.sno=score.sno;
#15、查询所有学生的Sno、Cname和Degree列。
select student.sno,course.cname,score.degree from student
join score on score.sno=student.sno
join course on course.cno=score.cno;
#16、查询所有学生的Sname、Cname和Degree列。
select a.sname,b.cname,c.degree
from student as a,course as b,score as c
where a.sno = c.sno and b.cno = c.cno;
select sname,cname,degree from student join score on student.sno=score.sno  join course on course.cno=score.cno;
#17、 查询“95033”班学生的平均分。
select sno from student where class="95033";
select avg(degree) from score where sno in(select sno from student where class="95033");
#1.查询选修“3-105”课程的成绩高于“109”号同学成绩的所有同学的记录。
#20、查询score中选学多门课程的同学中分数为非最高分成绩的记录。
#选修多门课的学生
select sno,count(*) from score group by sno;
#找到最高分
select max(degree) from score
select * from score where sno in(select sno from score group by sno)and degree<(select max(degree) from score);
#21、 查询成绩高于学号为“109”、课程号为“3-105”的成绩的所有记录。
select degree from score where sno="109" and cno="3-105";
select degree from score where degree>(select degree from score where sno="109" and cno="3-105");
#22、查询和学号为108的同学同年出生的所有学生的Sno、Sname和Sbirthday列。
select left(sbirthday,4) as date from student;
select sno,sname,sbirthday from student where sbirthday like concat((select left(sbirthday,4) as date from student where sno="108"),"","%");
#23、查询“张旭“教师任课的学生成绩。
#1、从成绩表 查询学生成绩  
#2、条件是这个课程是 “张旭“教师任课
#A)从老师表 中查名字叫 张旭 编号
#B)根据老师编号 在课程表中找到对应的 课程
select  depart from teacher where tname="张旭";
select cno from course where depart=(select  depart from teacher where tname="张旭");
#24、查询选修某课程的同学人数多于5人的教师姓名。
select cno from score group by cno having count(*)>"5";
select tno from course where cno in(select cno from score group by cno having count(*)>"5");
select tname from teacher where tno=(select tno from course where cno in(select cno from score group by cno having count(*)>"5"));
#25、查询95033班和95031班全体学生的记录。
select * from student where class in(95033,95031);
#26、  查询存在有85分以上成绩的课程Cno.
select cno from score where degree>"85";
#27、查询出“计算机系“教师所教课程的成绩表。
select tno from teacher where depart="计算机系";
select cno from course where tno in(select tno from teacher where depart="计算机系");
select * from score where cno in(select cno from course where tno in(select tno from teacher where depart="计算机系"));
#29、查询选修编号为“3-105“课程且成绩至少高于选修编号为“3-245”的同学的Cno、Sno和Degree,并按Degree从高到低次序排序。
select max(degree) from score where cno="3-245";
select * from score where cno="3-105" and degree>(select max(degree) from score where cno="3-245") order by degree desc;
#30、查询选修编号为“3-105”且成绩高于选修编号为“3-245”课程的同学的Cno、Sno和Degree.
select * from score where cno="3-105" and degree>(select max(degree) from score where cno="3-245");
#31、 查询所有教师和同学的name、sex和birthday.
select sname,ssex,sbirthday from student 
union 
select tname,tsex,tbirthday from teacher;
#32、查询所有“女”教师和“女”同学的name、sex和birthday.
select sname,ssex,sbirthday from student where ssex="女"
union 
select tname,tsex,tbirthday from teacher where tsex="女";
#33、 查询成绩比该课程平均成绩低的同学的成绩表。
select * from score group by cno having degree<avg(degree);
#34、 查询所有任课教师的Tname和Depart.
select cno from score group by cno;
select tno from course where cno in(select cno from score group by cno);
select tname,depart from teacher where tno in(select tno from course where cno in(select cno from score group by cno));
#35 、 查询所有未讲课的教师的Tname和Depart. 
select tname,depart from teacher where tno not in(select tno from course where cno in(select cno from score group by cno));
#36、查询至少有2名男生的班号。
select class from student where ssex="男" group by class having count(*)>1;
#37、查询Student表中不姓“王”的同学记录。
select * from student where sname not like"王%";
#38、查询Student表中每个学生的姓名和年龄。
select sname,(2018-left(sbirthday,4)) as age from student;
#39、查询Student表中最大和最小的Sbirthday日期值。
select max(sbirthday),min(sbirthday) from student;
#40、以班号和年龄从大到小的顺序查询Student表中的全部记录。
select * from student order by class desc,(2018-left(sbirthday,4))  desc;
#41、查询“男”教师及其所上的课程。
select tno from teacher where tsex="男";
select teacher.tname,course.cname from teacher,course where course.tno in(select tno from teacher where tsex="男") and course.tno= teacher.tno;
#42、查询最高分同学的Sno、Cno和Degree列。
select max(degree) from score  ;
select * from score where degree=(select max(degree) from score);
#43、查询和“李军”同性别的所有同学的Sname.
select ssex from student where sname="李军";
select sname from student where ssex=(select ssex from student where sname="李军");
#44、查询和“李军”同性别并同班的同学Sname.
select class from student where sname="李军";
select sname from student where ssex=(select ssex from student where sname="李军") and class=(select class from student where sname="李军");
#45、查询所有选修“计算机导论”课程的“男”同学的成绩表。
select cno from course where cname="计算机导论";
select sno from student where ssex="男";
select * from score where sno in(select sno from student where ssex="男") and cno in(select cno from course where cname="计算机导论")