有一个"学生－课程"数据库，数据库中包括三个表：
(1) "学生"表Student由学号Sno、姓名Sname、性别Ssex、年龄Sage、所在系Sdept五个属性组成，可记为： Student(Sno,Sname,Ssex,Sage,Sdept) Sno 为关键字。
(2) "课程"表Course由课程号Cno、课程名Cname、选修课号Cpno、学分Ccredit四个属性组成，可记为： Course(Cno,Cname,Cpno,Ccredit) Cno为关键字。
(3) "学生选课"表SC由学号Sno、课程号Cno、成绩Grade三个属性组成，可记为： SC(Sno,Cno,Grade) (SNO, CNO) 为关键字。
create database student_course default character set utf8;
create table student(
sno bigint primary key auto_increment,
sname varchar(32) not null,
ssex boolean default 1,
sage int,
sdept varchar(32)
)engine=innodb default charset utf8;
create table course(
cno bigint primary key,
cname varchar(32) not null,
cpno bigint,
ccredit int
)engine=innodb default charset utf8;
create table sc(
sno bigint,
cno bigint,
grade int,
primary key(sno,cno)
)engine = innodb default charset utf8;
1、建立一个"学生"表Student，它由学号Sno、姓名Sname、性别Ssex、年龄Sage、所在系Sdept五个属性组成，其中学号属性不能为空，并且其值是唯一的。
create table student (
Sno bigint primary key auto_increment,
Sname varchar(32),
Ssex boolean default 1,
Sage int,
Sdept varchar(32)
)engine=innodb default charset = utf8;
2、向Student表增加"入学时间"列，其数据类型为日期型。
alter table student add column sdate date;
3、删除Student表
drop table if exists student;
4、查询全体学生的学号与姓名
select sname,sno from student;
5、查询全体学生的详细记录
select * from student;
6、查所有选修过课的学生的学号
select distinct sno from sc;
7、查所有年龄在20岁以下的学生姓名及其年龄
select sname,sage from student where age <20;
8、查考试成绩有不及格的学生的学号
select distinct sno from sc where score <60;
9、查询年龄在20至23岁之间的学生的姓名、系别、和年龄
select sname,sdept,sage from student where age between 20 and 23;
10、查所有姓刘的学生的姓名、学号和性别
select sname,sno,ssex from student where sname like '刘%';
11、查姓"欧阳"且全名为三个汉字的学生的姓名
select sname from student where sname like '欧阳_';
12、查询姓名中有李字的所有学生信息
select *from student where sname like '%李%';
13、查询选修了3号课程的学生的学号及其成绩，查询结果按分数的降序排列
select sno,grade from sc where cno = 3 order by grade desc;
14、计算1号课程的学生平均成绩
select avg(grade) from sc where cno = 1;
15、查询学习1号课程的学生最高分数
select max(grade) from sc where cno = 1;
16、查询与"刘晨"在同一个系学习的学生
select sdept from student where sname = '刘晨';
select sname from student where sname != '刘晨' and sdept = (1);
select sname from student where sname != '刘晨' and sdept = (select sdept from student where sname = '刘晨');
17、将一个新学生记录（学号：95020；姓名：陈冬；性别：男；所在系：IS；年龄：18岁）插入Student表中
insert into student(sno,sname,ssex,sdept,sage) values(95020,'陈冬',1,'IS',18);
18、将学生95001的年龄改为22岁
update student set age=22 where sno = 95001;
19、将计算机科学系全体学生的成绩置零
select sno from student where sdept = '计算机科学系';
update sc set grade = 0 where sno in (1);
update sc set grade = 0 where sno in (select sno from student where sdept = '计算机科学系);
20、删除学号为95019的学生记录
delete from student where sno = 95019;
21、删除计算机科学系所有学生的选课记录
select sno from student where sdept = '计算机科学系';
delete from sc where sno in(1);
delete from sc where sno in(select sno from student where sdept = '计算机科学系');
22、查询选修了课程名为"信息系统"的学生学号和姓名
select cno from course where cname = '信息系统';
select sno from sc where cno in(1);
select sno,sname from student where sno in(2);
select sno,sname from student where sno in (select sno from sc where cno in (select cno from course where cname = '信息系统'));
23、查询其他系中比IS系任一学生年龄小的学生名单。
select sage from student where sdept = 'IS';
select * from student where sdept !='IS' and sage < any(1);
select * from student where sdept !='IS' and sage < any(select sage from student where sdept = 'IS');
24、查询student表中的所有信息，将查询结果保存到当前数据库中的新数据表re_stu中。
create table re_stu as student;
insert into re_stu select * from student;
25查询出所有学生的学号、姓名、性别、年龄、所在系，而且请使用中文作为查询结果的各字段的名称
select sno '学号',sname '姓名',sage '年龄',sdept '所在系' from student;