编写SQL语句（快速回顾）

注：源自于《Java程序员面试秘笈》！

1.创建数据库MYDB

create database MYDB

2.创建学生表student (sno,sname,ssex,sage,sclass)

create table student(
    sno int primary key,
    sname varchar(8),
    ssex varchar(3),
    sage int,
    scalss varchar(6)
)

3.创建课程表course(cno,cname,ccredit)

create table course(
    cno int primary key,
    cname varchar(20),
    ccredit int
)

4.创建选课表SC(sno,cno,grade)

create table SC(
    sno int foreign key references student(sno),
    cno int foreign key references course(cno),
    grade int
)

5.添加数据

insert into student values (1,'李勇','男'，20, 'y01')
insert into student values (2,'刘晨','男'，21, 'y02')
insert into student values (3,'王敏','女'，19, 'y02')
insert into student values (4,'张力','男'，20, 'y05')

6.添加数据

insert into course values (1, '数据库', 5)
insert into course values (2, 'C语言', 5)
insert into course values (3, '开发模式', 5)

7.添加数据

insert into SC values (1,1,5)
insert into SC values (1,2,5)
insert into SC values (1,1,5)
insert into SC values (1,3,5)

8.查询全体同学的学号、姓名

select sno, sname
from student

9.查询全体同学的姓名学号班级（按顺序输出）

select sname,snao,sclass
from student

10.查询全体同学的记录（显示所有行）

select * from student

11.查询全体同学的姓名及出生年份

select sname , 2017 - sage
from student

12.查询全体同学姓名、出生年份、班级（班级要用小写字母LOWER函数）

select sname , 2017 - sage 出生年份, lower(sclass)
from student

13.查询全体同学的姓名、出生年份、所在班级，列为YearOfBirth

select sname, 2017 - sage YearOfBirth, sclass
from student

14.查询选课中学员的学号，并且去掉重复行，用distinct

select distinct sno
from sc

15.查询Y02班全体同学名单

select *
from student
where sclass = 'Y02'

16.查询考试不及格的同学学号

select sno
from sc
where grade < 60

17.查询所有年龄在20岁以下的同学的姓名及年龄

select sname,sage
from student
where sage < 20

18.查询年龄在19_{20岁（包括19}20）之间的同学姓名、班级、年龄。

select sname,sclass,sage
from student
where sage>=19 and sage<=20
where between 19 and 20

19.查询年龄不在19~20岁之间的同学的姓名、班级、年龄。

select sname,sclass,sage
from student
where sage not between 19 and 20 

20.查询不是Y02班和Y05班的同学的姓名、性别。

select sname,ssex
from student
where not sclass = 'Y02' and not sclass = 'Y05'

21.查询Y02班和Y05班的同学姓名、性别

select sname , ssex
from student
where sclass = 'Y02' or sclass = 'Y05'

22.查询所有姓刘的同学的姓名、学号、性别。

select sname, sno, ssex
from student
where sname like '刘%'

23.查询所有姓张且全名为2个汉字的学生姓名

select sname
from student
where sname like '张_'

24.某些学生未考试，查询缺少成绩的同学的学号和课程号

select sno,cno
from sc
where grade is null

25.查询所有有成绩的同学的学号、课程号和成绩

select sno,cno
from sc
where grade is not null

26.查询Y02班年龄在20岁以下的学生的姓名和年龄

select sname, sage
from student
where sclass = 'Y02' and sage < 20

27.查询选修1号课程的同学的学号和成绩，按降序排列。

select sno,grade
from sc
where cno = 1
order by grade desc

28.查询全体同学信息查询结果，按所在班级的班级名称降序排列，同级同学按年龄升序排列。

select * 
from student
order by sclass desc , sage asc

29.查询学员总人数

select count(*) from student

30.查询选修课程学员人数。

select count(*) from sc

31.统计1号课的学员平均成绩。

select avg(grade)
from sc
where cno = 1

32.求各个课程号及相应的选课人数 (重点)

select count(*)
from sc
group by cno

33.查询选修1号课的同学的最高成绩

select max(grade)
from sc
where cno = 1

34.查询选取1门以上课程的同学学号

select sno 
from sc 
group by sno having count(cno) > 1

35.查询每个学员及其选修课程情况

select sno,cno
from sc

36.查询每个学员及其选修课情况，对没有选课的也要输出其名字、学号、性别、班级

select a.sno, a.sname, a.sage, a.ssex, a.sclass, sc.cno, sc.grade
from student a left outer join sc 
on a.sno = sc.sno order by a.sname

37.查询选取2号课程且成绩在90分以上的同学。

select * 
from sc
where cno = 2 and grade > 90

38.查询每个同学学号姓名、选修课程名及成绩。

select a.sno, a.sname, sc.cno, sc.grade
from student a left outer join sc
on a.sno = sc.sno
order by sc.sno

39.查询与刘晨在一个班的同学

select sname from student
where sclass in (
    select sclass
    from student
    where sname = '刘晨'
)

40.选取C语言的同学学号和姓名

select sno , sname
from student
where sno in (
    select sno
    from sc
    where cno in (
        select cno
        from course
        where cname = 'C语言'
    )
)

41.查询其他班中比Y02班某一同学大的同学姓名和年龄。

select sname , sage
from student 
where sage > any (
    select sage 
    from student 
    where sclass = 'Y02'
) and sclass <> 'Y02'

42.查询其他班中比Y02班同学全部都大的同学姓名和年龄。

select sname , sage
from student 
where sage > all (
    select sage 
    from student 
    where sclass = 'Y02'
) and sclass <> 'Y02'

43.查询选取1号课程的学员的姓名。

select sname
from student
where sno in(
    select sno
    from sc
    where cno = 1
)

44.查询没有选取1号课程的学员的姓名。

select sname
from student
where sno not in (
    select sno
    from sc
    where cno = 1
)

45.查询Y02班同学及年龄不大于19的学员（union）。

select * 
from student
where sclass = 'Y02' union
select *
from student
where sage <= 19

46.查询选取1号课程或者2号课程的同学学号

select distinct sno
from sc
where cno = 1 or cno = 2

47.将4号学员的年龄改为23岁。

update student set sage = 23 where sno = 4

48.将所有同学的年龄增加1岁

update student set sage = sage + 1

49.Y02班同学的成绩改为100分

update sc set grade = 100 
where sno in (
    select sno
    from student
    where sclass = 'y02'
)

50.删除学号为1的同学记录。

delete from student where sno = 1