Mysql student table common operations (3)

1. Topic

学生选课系统
1. 创建学生选课系统
2. 切换数据库
3. 创建学生表 TbStudent
    主键stuid ，姓名stuname，
    性别stusex，生日stubirth，电话stutel，住址stuaddr
    照片stuphoto（以二进制存）
4. 创建课程表TbCourse
主键cosid， 班级名称cosname，学分coscredit，课程描述cosintro
5. 学生选课记录表TbSC
主键scid，学生外键sid ，班级外键cid，创建日期scdate， 分数score

2. Create a student database

create database student;

use student;

-- 创建学生表
create table tbstudent 
( 
stuid integer not null,
stuname varchar(20) not null,
stusex bit default 1,
stubirth datetime not null,
stutel varchar(11),
stuaddr varchar(255),
stuphoto  longblob,
primary key (stuid)
);

-- 如果TBCourse已经存在就删除它
drop table if exists TbCourse;

-- 创建课程表
create table TbCourse
(
cosid integer not null,
cosname varchar(50) not null,
coscredit tinyint not null,
cosintro varchar(255)
);

-- 给课程表指定主键
alter table TbCourse add constraint pk_course primary key (cosid);

-- 创建学生选课记录表
create table tbSC 
(
scid integer primary key auto_increment,
sid integer not null,
cid integer,
scdate datetime not null,
score float
);

-- 给表TBSC添加外键约束
alter table TbSC add constraint fk_sid foreign key (sid) references TbStudent (
stuid) on delete cascade on update cascade;
alter table TbSC add constraint fk_cid foreign key (cid) references TBCourse (
cosid) on delete set null on update cascade;

3. Add data

-- 添加学生记录
insert into TBStudent values (1001, '张三丰', default, '1978-1-1', '12345678907','成都市一环路西二段17号', null);
insert into TBStudent (stuid, stuname, stubirth) values (1002, '郭靖', '1980-2-2');
insert into TBStudent (stuid, stuname, stusex, stubirth, stuaddr) values (1003, '黄蓉', 0, '1982-3-3', '成都市二环路南四段123号');
insert into TbStudent values (1004, '张无忌', 1, '1990-4-4', null, null, null);
insert into TBStudent values
(1005, '丘处机',1, '1983-5-5', '12345678907', '北京市海淀区宝盛北里西区34号', null),
(1006, '王处一',1, '1985-6-6', '12345678906','深圳市海淀区宝盛北里西区34号', null),
(1007, '刘处玄',1, '1987-7-7', '12345678904','郑州市海淀区宝盛北里西区34号', null),
(1008, '孙不二',0, '1989-8-8', '12345678903','武汉市海淀区宝盛北里西区34号', null),
(1009, '平一指',1, '1992-9-9', '12345678902','西安海淀区宝盛北里西区34号', null),
(1010, '老不死',1, '1993-10-10', '12345678901','广州市海淀区宝盛北里西区34号', null),
(1011, '王大锤',0, '1994-11-11', '12345678917',null, null),
(1012, '隔壁老王',1, '1995-12-12', '12345678207',null, null),
(1013, '郭啸天',1, '1977-10-25', '12345678922',null, null);


-- 添加课程记录
insert into TbCourse values
(1111, 'C语言程序设计',3, '大神级讲师授课需要抢座'),
(2222, 'java程序设计', 3, null),
(3333, '数据库概论', 2, null),
(4444, '操作系统原理', 4, null);


-- 添加学生选课记录
insert into tbSC values
(default, 1001, 1111, '2016-9-1', 95),
(default, 1002, 1111, '2016-9-1', 95),
(default, 1001, 2222, now(), 95),
(default, 1001, 3333, '2017-3-1', 85),
(default, 1001, 4444, now(), null),
(default, 1002, 4444, now(), null),
(default, 1003, 2222, now(), null),
(default, 1003, 3333, now(), null),
(default, 1005, 2222, now(), null),
(default, 1006, 1111, now(), null),
(default, 1006, 2222, '2017-3-1', null),
(default, 1006, 3333, now(), null),
(default, 1006, 4444, now(), null),
(default, 1007, 1111, '2016-9-1', null),
(default, 1007, 3333, now(), null),
(default, 1007, 4444, now(), null),
(default, 1008, 2222, now(), null),
(default, 1010, 1111, now(), null);

4. Operations on the database

-- 查询所有学生信息
select * from TbStudent;


-- 查询所有课程名称及学分(投影和别名)
select cosname as `课程名称`, coscredit as `学分` from TbCourse;


-- 查询所有女学生的姓名和出生日期(筛选)
select stuname, stubirth from TbStudent where stusex=0;


-- 查询所有80后学生的姓名、性别和出生日期(筛选)
select stuname as `姓名`, if(stusex, '男', '女') as `性别`, stubirth as `出生日期`
from TbStudent where stubirth between '1980-1-1' and '1989-12-31';


-- 查询姓王的学生姓名和性别(模糊)
select stuname, stusex from TbStudent where stuname like '王%';


-- 查询姓郭名字总共两个字的学生的姓名(模糊)
select stuname from TbStudent where stuname like '郭_';


-- 查询姓郭名字总共三个字的学生的姓名(模糊)
select stuname from TbStudent where stuname like '郭__';


-- 查询名字中有王字的学生的姓名(模糊)
select stuname from TbStudent where stuname like '%王%';


-- 查询没有录入家庭住址和照片的学生姓名(多条件筛选和空值处理)
select stuname from TbStudent where stuaddr is null and stuphoto is null;


-- 查询学生选课的所有日期(去重)
select distinct scdate from TbSC;


-- 查询学生的姓名和生日按年龄从大到小排列(排序)
select stuname, stubirth from TbStudent order by stubirth;


-- 查询所有录入了家庭住址的男学生的姓名、出生日期和家庭住址按年龄从小到大排列(多条件筛选和排序)
select stuname, stubirth, stuaddr from TbStudent where stusex=1 and stuaddr is not null order by stubirth desc;


-- 查询年龄最大的学生的出生日期(聚合函数)
select min(stubirth) from TbStudent;


-- 查询年龄最小的学生的出生日期(聚合函数)
select max(stubirth) from TbStudent;


-- 查询男女学生的人数(分组和聚合函数)
select if(stusex, '男', '女') as `性别`, count(stusex) as `人数` from TbStudent group by stusex;


-- 查询课程编号为1111的课程的平均成绩(筛选和聚合函数)
select avg(score) as `平均成绩` from TbSC where cid=1111;


-- 查询学号为1001的学生所有课程的总成绩(筛选和聚合函数)
select sum(score) as `总成绩` from TbSC where sid=1001;


-- 查询每个学生的学号和平均成绩, null值处理成0(分组和聚合函数)
select sid as `学号`, ifnull(avg(score), 0) as `平均成绩` from TbSC group by sid;


-- 查询平均成绩大于等于90分的学生的学号和平均成绩
select sid as `学号`, avg(score) as `平均成绩` from TbSC group by sid having avg(score)>=90;


-- 查询年龄最大的学生的姓名(子查询)
select stuname from TbStudent where stubirth=(select min(stubirth) from TbStudent);


-- 查询选了两门以上的课程的学生姓名(子查询/分组条件/集合运算)
select stuname from TbStudent where stuid in 
(select sid from TbSC group by sid having count(sid)>2);


-- 查询选课学生的姓名和平均成绩(子查询和连接查询)
-- 写法1:
select stuname, avgscore from TbStudent t1 inner join
(select sid, avg(score) as avgscore from TbSC where score is not null group by sid) t2
on t1.stuid=t2.sid;
-- 写法2: 
select stuname, avgscore from TbStudent t1,
(select sid, avg(score) as avgscore from TbSC where score is not null group by sid) t2
where t1.stuid=t2.sid;


-- 查询学生姓名、所选课程名称和成绩(连接查询)
-- 写法1:
select stuname, cosname, score from 
TbStudent t1, TbCourse t2, TbSC t3
where t1.stuid=t3.sid and t2.cosid=t3.cid and t3.score is not null;
-- 写法2:
select stuname, cosname, score from TbStudent t1 inner join TbCourse t2
inner join (select sid, cid, score from TbSC where score is not null) t3 
on t1.stuid=t3.sid and t2.cosid=t3.cid;


-- 查询每个学生的姓名和选课数量(左外连接和子查询)
select stuname as `姓名`, ifnull(coscount, 0) as `选课数` from TbStudent t1
left outer join (select sid, count(sid) as coscount from TbSC group by sid) t2 
on t1.stuid=t2.sid;