topic
Existing class, student achievement as well as three tables:
NOTE: The table names and field names can refer to the set of words within a table
According to the table information, as required to complete the following SQL statement to write:
1, respectively, using SQL to create a class table, table structure and table student achievement table within a table data can be inserted into a bulk insert
2, query each class in average scores of each subject, display data includes the name of the class, course, and the average score, and arranged in ascending order Class ID
3, query for all students student ID, name, gender, and total score, according to results from high to low and sort
4, students inquire course grade less than 75 points of ID, name, class, courses and scores
5, Li Mimi math revised to 88
6, key classes in computing the average score for each department, including data display: the focus of the class ID, class name, course, mean scores, in descending order
answer
create database if not exists mooc default character set 'utf8';
use mooc;
--班级表
create table if not exists class(
c_id int(3) unsigned zerofill auto_increment key comment '编号',
name varchar(20) not null comment '班级',
descrip varchar(20) not null comment '备注'
)engine=innodb charset=utf8;
--插入班级数据
insert class(name,descrip)
values('一年级一班','重点班'),
('一年级二班','重点班'),
('二年级一班','重点班'),
('二年级二班','普通班');
--学生表
create table if not exists student(
s_id int unsigned auto_increment key comment '编号',
name varchar(20) not null comment '姓名',
gender varchar(5) not null comment '性别',
class int(3) unsigned zerofill not null comment '班级'
)engine=innodb charset=utf8;
alter table student auto_increment=1001; --修改主键初始值
--插入学生数据
insert student(name,gender,class)
values('赵晓明','男','001'),
('王晓红','女','001'),
('张晓晓','女','001'),
('孙琪琪','女','003'),
('李米米','女','004'),
('赵晓刚','男','003'),
('张大宝','男','002'),
('张兰','女','004'),
('孙好','男','001');
--成绩表
create table if not exists score(
sc_id int(3) unsigned zerofill auto_increment key comment '编号',
s_id int unsigned not null comment '学生ID',
course varchar(10) not null comment '课程',
mark int unsigned not null comment '分数'
)engine=innodb charset=utf8;
--插入成绩数据
insert score(s_id,course,mark)
values(1001,'数学',98),
(1001,'语文',90),
(1001,'英语',97),
(1002,'数学',96),
(1002,'语文',88),
(1003,'语文',88),
(1002,'英语',91),
(1003,'数学',96),
(1003,'英语',86),
(1004,'数学',89),
(1004,'语文',82),
(1004,'英语',83),
(1005,'数学',75),
(1005,'语文',86),
(1005,'英语',77),
(1006,'数学',81),
(1006,'语文',77),
(1006,'英语',60),
(1007,'数学',89),
(1007,'语文',56),
(1007,'英语',70),
(1008,'数学',87),
(1008,'语文',55),
(1008,'英语',66),
(1009,'数学',78),
(1009,'语文',60),
(1009,'英语',52);
--添加外键约束
alter table student add foreign key(class) references class(c_id);
alter table score add foreign key(s_id) references student(s_id);
--查询每个班级中每一科的平均成绩，显示数据包括班级名称，
--课程以及平均分数，并按照班ID升序排列
select c.name as 班级名称,sc.course as 课程,avg(mark) as 平均分
from class as c
inner join student as st
on c.c_id = st.class
inner join score as sc
on st.s_id = sc.s_id
group by 班级名称,课程
order by 班级名称;
+------------+------+---------+
| 班级名称 | 课程 | 平均分 |
+------------+------+---------+
| 一年级一班 | 数学 | 92.0000 |
| 一年级一班 | 英语 | 81.5000 |
| 一年级一班 | 语文 | 81.5000 |
| 一年级二班 | 数学 | 89.0000 |
| 一年级二班 | 英语 | 70.0000 |
| 一年级二班 | 语文 | 56.0000 |
| 二年级一班 | 数学 | 85.0000 |
| 二年级一班 | 英语 | 71.5000 |
| 二年级一班 | 语文 | 79.5000 |
| 二年级二班 | 数学 | 81.0000 |
| 二年级二班 | 英语 | 71.5000 |
| 二年级二班 | 语文 | 70.5000 |
+------------+------+---------+
--查询所有同学的学生ID，姓名，
--性别以及总分，并按照成绩从高到低排序
select st.s_id as 学生ID,st.name as 姓名,st.gender as 性别,sum(mark) as 总分
from student as st
inner join score as sc
on st.s_id = sc.s_id
group by 学生ID
order by 总分 desc;
+--------+--------+------+------+
| 学生ID | 姓名 | 性别 | 总分 |
+--------+--------+------+------+
| 1001 | 赵晓明 | 男 | 285 |
| 1002 | 王晓红 | 女 | 275 |
| 1003 | 张晓晓 | 女 | 270 |
| 1004 | 孙琪琪 | 女 | 254 |
| 1005 | 李米米 | 女 | 238 |
| 1006 | 赵晓刚 | 男 | 218 |
| 1007 | 张大宝 | 男 | 215 |
| 1008 | 张兰 | 女 | 208 |
| 1009 | 孙好 | 男 | 190 |
+--------+--------+------+------+
--查询课程成绩小于75分的学生ID，姓名，班级，课程以及分数
select st.s_id as 学生ID,st.name as 姓名,st.class as 班级,sc.course as 课程,sc.mark as 分数
from student as st
inner join class as c
on c.c_id = st.class
inner join score as sc
on sc.s_id = st.s_id
where sc.mark < 75;
+--------+--------+------+------+------+
| 学生ID | 姓名 | 班级 | 课程 | 分数 |
+--------+--------+------+------+------+
| 1009 | 孙好 | 001 | 语文 | 60 |
| 1009 | 孙好 | 001 | 英语 | 52 |
| 1007 | 张大宝 | 002 | 语文 | 56 |
| 1007 | 张大宝 | 002 | 英语 | 70 |
| 1006 | 赵晓刚 | 003 | 英语 | 60 |
| 1008 | 张兰 | 004 | 语文 | 55 |
| 1008 | 张兰 | 004 | 英语 | 66 |
+--------+--------+------+------+------+
--将李米米的数学成绩修改为88分
update score set mark = 88 where s_id =
(select s_id from student where name = '李米米')
and course = '数学';
--计算重点班中每一科的平均成绩，显示数据包括：
--重点班级ID，班级名称，课程，平均分数，按照降序排列
select c.c_id as 重点班级ID,c.name as 班级名称,sc.course as 课程,avg(mark) as 平均分
from class as c
inner join student as st
on c.c_id = st.class
inner join score as sc
on st.s_id = sc.s_id
where c.descrip = '重点班'
group by 班级名称,课程;
+------------+------------+------+---------+
| 重点班级ID | 班级名称 | 课程 | 平均分 |
+------------+------------+------+---------+
| 001 | 一年级一班 | 数学 | 92.0000 |
| 001 | 一年级一班 | 语文 | 81.5000 |
| 001 | 一年级一班 | 英语 | 81.5000 |
| 002 | 一年级二班 | 数学 | 89.0000 |
| 002 | 一年级二班 | 语文 | 56.0000 |
| 002 | 一年级二班 | 英语 | 70.0000 |
| 003 | 二年级一班 | 数学 | 85.0000 |
| 003 | 二年级一班 | 语文 | 79.5000 |
| 003 | 二年级一班 | 英语 | 71.5000 |
+------------+------------+------+---------+