作业

准备数据

create table book(
	id int primary key auto_increment,
	name varchar(16),
	price int
);
create table author(
	id int primary key auto_increment,
	name varchar(16)
);
create table book_author(
    id int primary key auto_increment,
    book_id int,
    author_id int
);

id	name	pirce
1	葵花宝典	88
2	九阴真经	78
3	辟邪剑谱	99

id	name
1	张全蛋
2	李诞
3	寡人

id	book_id	author_id
1	1	1
2	1	2
3	1	3
4	2	1
5	2	3
6	3	2
7	3	2

2、查看每本书的作者

3、查看每位作者都有哪些作品

4、利用pymysql操作数据库实现sql注入效果

5、利用pymysql实现登陆注册功能

登陆:展示对应的错误信息(用户名错误，密码错误)

import pymysql

class Mysql:
    def __init__(self):
        self.conn = pymysql.connect(
            host = '127.0.0.1',
            port = 3306,
            user = 'root',
            password = '123',
            database = 'day41',
            charset = 'utf8'
        )
        self.cursor = self.conn.cursor()

    def select(self,name,table):
        sql = "select * from {} where sname = %s".format(table)
        self.cursor.execute(sql,(name,))
        return self.cursor.fetchall()





mysql = Mysql()
res = mysql.select('egon','student')
print(res)






conn = pymysql.connect(
    host='127.0.0.1',
    port=3306,
    database='day41',
    charset ='utf8',
    user='root',
    password='123'
)

cursor = conn.cursor(pymysql.cursors.DictCursor)

sql = 'select * from student'

size = cursor.execute(sql)
print(size)

data = cursor.fetchone()
data2 = cursor.fetchone()
data3 = cursor.fetchall()
print(data,data2,data3)
sql = "insert into student(gender,sname,class_id) values('女','yaya','2') "
cursor.execute(sql)
conn.commit()

-- 1、查询所有的课程的名称以及对应的任课老师姓名
-- SELECT course.cname,teacher.tname from course INNER JOIN teacher on course.teacher_id = teacher.tid;
-- 2、查询学生表中男女生各有多少人
-- select gender,count(sid) from student GROUP BY gender;

-- 3、查询物理成绩等于100的学生的姓名
-- select sname from student where sid in
-- (SELECT student_id from score where num=100 and course_id in
-- (SELECT course_id from score INNER JOIN course on score.course_id = course.cid where cname='物理'));
-- 4、查询平均成绩大于八十分的同学的姓名和平均成绩
-- select student.sname,t1.avg_num from student INNER JOIN
-- (SELECT student_id,avg(num)as avg_num from score GROUP BY student_id HAVING avg(num)>80)as t1 on student.sid = t1.student_id;
-- 5、查询所有学生的学号，姓名，选课数，总成绩
-- select sid,sname,count_course,sum_num from student INNER JOIN
-- (select student_id,count(course_id)as count_course,sum(num)as sum_num from score GROUP BY student_id)as t1 on student.sid = t1.student_id;

-- 6、查询姓李老师的个数
-- SELECT COUNT(tname) FROM teacher WHERE tname LIKE '%李%'

-- 7、查询没有报李平老师课的学生姓名
-- select sname from student where sid not in
-- (select student_id from score where course_id in
-- (select cid from teacher INNER JOIN course on course.teacher_id = teacher.tid where teacher.tname='李平老师'));
-- 8、查询物理课程比生物课程高的学生的学号
-- select student_id from
-- (select student_id,num from score where course_id in
-- (select cid from course where cname='物理'))as t1 INNER JOIN
-- (select student_id as id,num from score where course_id in
-- (select cid from course where cname='生物')) as t2
-- on t1.student_id = t2.id

-- where t1.num>t2.num;

-- -- 第二种方法
-- SELECT
-- t1.student_id
-- FROM
-- (
-- SELECT
-- student_id,
-- num
-- FROM
-- score
-- WHERE
-- course_id = (
-- SELECT
-- cid
-- FROM
-- course
-- WHERE
-- cname = '物理'
-- )
-- ) AS t1
-- INNER JOIN (
-- SELECT
-- student_id,
-- num
-- FROM
-- score
-- WHERE
-- course_id = (
-- SELECT
-- cid
-- FROM
-- course
-- WHERE
-- cname = '生物'
-- )
-- ) AS t2 ON t1.student_id = t2.student_id
-- WHERE
-- t1.num > t2.num;

-- 9、查询没有同时选修物理课程和体育课程的学生姓名
-- select sname from student where sid in
-- (select student_id from score where course_id in
-- (select cid from course where cname='体育' or cname='物理') GROUP BY student_id HAVING count(course_id)=1);

--
-- 10、查询挂科超过两门(包括两门)的学生姓名和班级
-- select sname,caption from class INNER JOIN student on class.cid = student.class_id where sid in
-- (select student_id from score INNER JOIN course on score.course_id = course.cid where score.num<60 GROUP BY student_id having count(course_id)>=2);

-- 11、查询选修了所有课程的学生姓名
-- select student.sname from student WHERE sid in
-- (SELECT student_id from score GROUP BY student_id having count(course_id) = (select count(cid) from course));

-- 12、查询李平老师教的课程的所有成绩记录
-- select num from score where course_id in
-- (select cid from course INNER JOIN teacher on course.teacher_id = teacher.tid where tname = '李平老师');

-- 13、查询全部学生都选修了的课程号和课程名
-- select cid,cname from course where cid in
-- (select course_id from score GROUP BY course_id HAVING count(student_id)=(select count(sid) from student));

-- 14、查询每门课程被选修的次数
-- select course_id,count(student_id) from score GROUP BY course_id;

-- 15、查询之选修了一门课程的学生姓名和学号
-- select sid,sname from student where sid in
-- (select student_id from score GROUP BY student_id HAVING count(course_id)=1);
-- 16、查询所有学生考出的成绩并按从高到低排序（成绩去重）
-- select distinct num from score ORDER BY num desc;

-- 17、查询平均成绩大于85的学生姓名和平均成绩
-- select sname,avg_num from student INNER JOIN
-- (select student_id,avg(num)as avg_num from score GROUP BY student_id HAVING avg(num)>85)as t1 on student.sid = t1.student_id ;
-- 18、查询生物成绩不及格的学生姓名和对应生物分数
select sname,num from student INNER JOIN
(select student_id,num from score where course_id=

(select cid from course where cname='生物')and num<60)as t1
on student.sid = t1.student_id
Time: 0.001s

[2019-05-18 18:13:20.11][localhost_3306][000037][MYSQL]
-- 19、查询在所有选修了李平老师课程的学生中，这些课程(李平老师的课程，不是所有课程)平均成绩最高的学生姓名‘

select sname from student where sid =(
-- SELECT student_id from score where course_id in
-- (select cid from course INNER JOIN teacher on course.teacher_id = teacher.tid where tname='李平老师')group by student_id order by avg(num) desc limit 1);

-- 20、查询每门课程成绩最好的前两名学生姓名

SELECT
score.student_id,
t3.course_id,
t3.first_num,
t3.second_num
FROM
score
INNER JOIN (
SELECT
t1.course_id,
t1.first_num,
t2.second_num
FROM
(
SELECT
course_id,
max(num) first_num
FROM
score
GROUP BY
course_id
) AS t1
INNER JOIN (
SELECT
score.course_id,
max(num) second_num
FROM
score
INNER JOIN (
SELECT
course_id,
max(num) first_num
FROM
score
GROUP BY
course_id
) AS t ON score.course_id = t.course_id
WHERE
score.num < t.first_num
GROUP BY
course_id
) AS t2 ON t1.course_id = t2.course_id
) AS t3 ON score.course_id = t3.course_id
WHERE
score.num = t3.second_num
or score.num = t3.first_num
ORDER BY
course_id

-- 21、查询不同课程但成绩相同的学号，课程号，成绩

-- 22、查询没学过“叶平”老师课程的学生姓名以及选修的课程名称；

select student_id,t1.cname from score INNER JOIN
(select cid,cname from course INNER JOIN teacher on course.teacher_id = teacher.tid where teacher.tname='李平老师')as t1 on score.course_id= t1.cid;

-- 23、查询所有选修了学号为1的同学选修过的一门或者多门课程的同学学号和姓名；

-- 24、任课最多的老师中学生单科成绩最高的学生姓名

select sname from student where student.sid in
(select student_id from score where num in
(select max(num) from score where course_id in
(select cid from course where teacher_id =
(select tid from teacher INNER JOIN course on course.teacher_id = teacher.tid GROUP BY tid ORDER BY count(teacher_id) desc limit 1))GROUP BY course_id))

作业