MySQL数据库_(学生_教师_课程_成绩)表_练习
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SQL的执行顺序
(8) SELECT (9) DISTINCT column,... 选择字段、去重
(6) AGG_FUNC(column or expression),... 聚合
(1) FROM [left_table] 选择表
(3) <join_type> JOIN <right_table> 链接
(2) ON <join_condition> 链接条件
(4) WHERE <where_condition> 条件过滤
(5) GROUP BY <group_by_list> 分组
(7) HAVING <having_condition> 分组过滤
(9) ORDER BY <order_by_list> 排序
(10) LIMIT count OFFSET count; 分页
/*==============================================================*/
/* Table: teachers */
/*==============================================================*/
drop table if exists teachers;
create table teachers(
tno varchar(3) not null,
tname varchar(4),
tsex varchar(2),
tbirthday datetime,
prof varchar(6),
depart varchar(10),
primary key (tno)
);
/*==============================================================*/
/* Table: students */
/*==============================================================*/
drop table if exists students;
create table students
(
sno varchar(3) not null,
sname varchar(4) not null,
ssex varchar(2) not null,
sbirthday datetime,
class varchar(5),
primary key (sno)
);
/*==============================================================*/
/* Table: courses */
/*==============================================================*/
drop table if exists courses;
create table courses
(
cno varchar(5) not null,
cname varchar(10) not null,
tno varchar(3) not null,
primary key (cno)
);
alter table courses add constraint FK_Reference_3 foreign key(tno)
references teachers(tno) on delete restrict on update restrict;
/*==============================================================*/
/* Table: scores */
/*==============================================================*/
drop table if exists scores;
create table scores
(
sno varchar(3) not null,
cno varchar(5) not null,
degree numeric(10,1) not null,
primary key (sno, cno)
);
alter table scores add constraint FK_Reference_1 foreign key(sno)
references students(sno) on delete restrict on update restrict;
alter table scores add constraint FK_Reference_2 foreign key(cno)
references courses(cno) on delete restrict on update restrict;
# 考试题型
# 查看一张表中的所有记录(studnets)
select * from students;
# 查询一张表中的指定列(students(学号,名字))
select sno,sname from students;
# 查询指定的记录(students(学号=101))
select * from students where sno=101;
# 模糊查询--查询1976年出生的学生
select * from students where sbirthday like '1976-%'
# 模糊查询--查询70后的学生
select * from students where sbirthday like '197%'
# 查询某个范围之间的所有记录
select * from students as s where s.sno between 101 and 107;
# 查询满足多个条件的记录 and or in
select * from students as s where s.ssex = '男' and s.class ='95033';
select * from students as s where s.sno = 101 or s.sno=103;
select * from students as s where s.class in (95031,95033);
# 去重 distinct
select distinct s.class from students as s
# 按学号升降 查询记录
select * from students as s order by s.sno asc;
select * from students as s order by s.sno desc;
# 查询每个班的人数
select class,count(class) from students group by class;
select stu.class,count(stu.class) from students as stu group by class
# 查询学生中最大和最小出生日期与姓名
select stu.sname,stu.sbirthday from students as stu
where
stu.sbirthday = (
select max(sbirthday) from students
)
OR
stu.sbirthday = (
select min(sbirthday) from students
)
# 查询每个课程的评价成绩
select cno,avg(degree) from scores
group by cno
# 查询男教师及其所上的课程
select * from teachers as a inner join courses as b
on a.tno = b.tno and a.tsex='男'
# 查询每个老师教的课程
select * from teachers as t
left join courses as c
on t.tno = c.tno
# 查询女老师的信息
select *
from teachers as t
left join courses as c
on t.tno = c.tno
where t.tsex = '女'
# 查询得分前3名的学员信息
select *
from students as s
where s.sno in (
select a.sno from
(select sc.sno
from scores as sc
order by sc.degree
limit 3 )as a
)
# 查询课程是“计算机导论”的,得分前3名的学员信息
select *
from scores
where cno = (
select cno from courses where cname='计算机导论'
)
order by degree desc limit 3
select * from scores where cno='3-105' order by degree limit 3
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