实验三:
select sno,sname
from student;//（1）查询全体学生的学号和姓名
select *
from student;//（2）查询全体学生的详细记录
select sname,sage,sdept
from student where sdept=‘MA‘;//（3）查询软件学院的学生姓名、年龄、系别
select distinct sno
from sc;//（4）查询所有选修过课程的学生学号（不重复）
select distinct sno
from sc
where grade<60;//（5）查询考试不及格的学生学号（不重复）
select ssex,sage,sdept
from student
where sdept not in(‘CS‘,‘MA‘);//（6）查询不是软件学院、计算机系的学生性别、年龄、系别
select sno,sname,sdept,sage
from student
where sage>=18 and sage<=20;//（7）查询年龄18－20岁的学生学号、姓名、系别、年龄；
select *
from student
where sname like ‘刘%‘;//（8）查询姓刘的学生情况
select *
from student
where sname like ‘刘%‘or sname like ‘李%‘;//（9）查询姓刘或姓李的学生情况
select *
from student
where sname like ‘刘_‘;//（10）查询姓刘且名字为两个字的学生情况
select sname
from student
where sage<31;//（11）查询1983年以后出生的学生姓名。
create table studentgrade
(
sno char(8) PRimary key,
mathgrade tinyint,
englishgrade tinyint,
chinesegrade tinyint
)
go
insert into studentgrade(sno,mathgrade,englishgrade,chinesegrade) values( ‘95001‘,85,95,74)
insert into studentgrade(sno,mathgrade,englishgrade,chinesegrade) values( ‘95002‘,86,91,70)
insert into studentgrade(sno,mathgrade,englishgrade,chinesegrade) values( ‘95003‘,80,92,71)
insert into studentgrade(sno,mathgrade,englishgrade,chinesegrade) values( ‘95004‘,81,91,75)
insert into studentgrade(sno,mathgrade,englishgrade,chinesegrade) values( ‘95005‘,87,97,78)
insert into studentgrade(sno,mathgrade,englishgrade,chinesegrade) values( ‘95006‘,81,97,70)
insert into studentgrade(sno,mathgrade,englishgrade,chinesegrade) values( ‘95007‘,85,95,70)
select sum(mathgrade+englishgrade+chinesegrade) as sumgrades
from studentgrade group by sno;（12）创建表 studentgrade(sno,mathgrade,englishigrade,chinesegrade)
计算学生各科总成绩并赋予别名
select (year(getdate())-student.sage+1)
from student
where sdept=‘MA‘;//（13）利用内部函数 year()查找软件学院学生的出生年份
select sname + ‘年龄为‘+cast(sage as char(2))+‘岁‘
from student;
Select sname + ‘年龄为’+cast(sage as char(2))+’岁’
From student//（14）利用字符转换函数实现字符联接。
select*
from student order by sdept,sage desc;//（15）查询全体学生情况，查询结果按所在系升序排列，对同一系中的学生按年龄降序排列。
select count(*)
from student;//查询总人数
select count(distinct sno)
from sc;//查询选修了课程的学生人数
select count(*),avg(grade)as avggrade
from student ,sc
where student.sno=sc.sno and sc.cno=‘1‘;//（18）查询选修了7号课程的学生总人数和平均成绩
select max(grade) as maxgrade
from sc
where cno=‘2‘;//（19）查询选修6号课程学生的最好成绩
select sdept,count(*)
from student group by sdept;//（20）查询每个系的系名及学生人数。
select cno,count(*),avg(grade) as avggrade
from sc group by cno;//（21）查找每门课的选修人数及平均成绩
select *
from course
where cpno is null;//（22）查找没有先修课的课程情况