django模型系统（三）

1，自定义主键字段的创建

　　AutoFiled(pirmary_key=True)  # 一般不会自定义

2，order_by  asc  desc

表关系

OneToOne

student = models.OneToOneField('Student' , on_delete=models.CASCADE)  #一对一的核心代码

(mysite) pyvip@VIP:~/python34/mysite$ python manage.py makemigrations   #根目录下运行

(mysite) pyvip@VIP:~/python34/mysite$ python manage.py migrate

(py3env) pyvip@VIP:~$ mysql -A mysite -uroot -pqwe123  #进入数据库

OneToMany

grade = models.ForeignKey('Grade', on_delete=models.SET_NULL, null=True)  #一对多核心代码

ManyToMany

2，关联表的数据操作

　　OneToMany

正向 ：一个模型如果定义了一个外键字段，通过这个模型操作外键

删除必须有null

增删改查

In [29]: g3 = Grade.objects.create(name='进阶', num='40期')

In [30]: g3.student_set.create(name='李鹏辉')
Out[30]: <Student: 李鹏辉-0>

In [31]: g3.student_set.add(s)    add立刻马上执行，不用操作数据库

有clear方法先执行clear再添加，如果clear没有就直接添加

只要是返现就模型的小写加上s-set

Many-to-Many

*****指定了中间表，add， remove， set 都不能用，必须用中间表

正向：

In [78]: c1.students.all()
Out[78]: <QuerySet [<Student: 心蓝-0>, <Student: 心蓝-0>, <Student: 李鹏辉-0>]>

反向：

In [79]: s1.course_set.all()
Out[79]: <QuerySet [<Course: python全栈>, <Course: java>, <Course: python全栈>]>

One—to—One

In [85]: sd = StudentDetail.objects.create(num='2019020001', college='家里蹲', student=s1)

In [86]: sd
Out[86]: <StudentDetail: StudentDetail object (1)>

In [87]: sd.student
Out[87]: <Student: 心蓝-0>

In [88]: sd.student.name
Out[88]: '心蓝'

In [89]: sd.student.age
Out[89]: 0

In [90]: s1.studentdetail
Out[90]: <StudentDetail: StudentDetail object (1)>

In [91]: s1.studentdetail.num
Out[91]: '2019020001'

In [92]: s1.studentdetail.college
Out[92]: '家里蹲'

跨表查询

In [93]: res = Course.objects.filter(students__sex=1)

In [94]: print(res.query)
SELECT `teacher_course`.`id`, `teacher_course`.`name` FROM `teacher_course` INNER JOIN `teacher_enroll` ON (`teacher_course`.`id` = `teacher_enroll`.`course_id`) INNER JOIN `teacher_student` ON (`teacher_enroll`.`student_id` = `teacher_student`.`id`) WHERE `teacher_student`.`sex` = 1

In [95]: res = Student.objects.filter(course__name__contain='python')

In [96]: print(res.query)
SELECT `teacher_student`.`id`, `teacher_student`.`name`, `teacher_student`.`age`, `teacher_student`.`sex`, `teacher_student`.`qq`, `teacher_student`.`phone`, `teacher_student`.`grade_id`, `teacher_student`.`c_time`, `teacher_student`.`e_tine` FROM `teacher_student` INNER JOIN `teacher_enroll` ON (`teacher_student`.`id` = `teacher_enroll`.`student_id`) INNER JOIN `teacher_course` ON (`teacher_enroll`.`course_id` = `teacher_course`.`id`) WHERE `teacher_course`.`name` LIKE BINARY %python%

In [99]: res = Student.objects.filter(course__name__contains='english',grade__num__contains='33')

In [100]: print(res.query)
SELECT `teacher_student`.`id`, `teacher_student`.`name`, `teacher_student`.`age`, `teacher_student`.`sex`, `teacher_student`.`qq`, `teacher_student`.`phone`, `teacher_student`.`grade_id`, `teacher_student`.`c_time`, `teacher_student`.`e_tine` FROM `teacher_student` INNER JOIN `teacher_enroll` ON (`teacher_student`.`id` = `teacher_enroll`.`student_id`) INNER JOIN `teacher_course` ON (`teacher_enroll`.`course_id` = `teacher_course`.`id`) INNER JOIN `teacher_grade` ON (`teacher_student`.`grade_id` = `teacher_grade`.`id`) WHERE (`teacher_course`.`name` LIKE BINARY %english% AND `teacher_grade`.`num` LIKE BINARY %33%)

In [101]: res = Student.objects.filter(enroll__pay__lt=3000)

In [102]: print(res.query)
SELECT `teacher_student`.`id`, `teacher_student`.`name`, `teacher_student`.`age`, `teacher_student`.`sex`, `teacher_student`.`qq`, `teacher_student`.`phone`, `teacher_student`.`grade_id`, `teacher_student`.`c_time`, `teacher_student`.`e_tine` FROM `teacher_student` INNER JOIN `teacher_enroll` ON (`teacher_student`.`id` = `teacher_enroll`.`student_id`) WHERE `teacher_enroll`.`pay` < 3000.0

In [103]: res = Grade.objects.filter(student__course__name__contains='python')

In [104]: print(res.query)
SELECT `teacher_grade`.`id`, `teacher_grade`.`name`, `teacher_grade`.`num` FROM `teacher_grade` INNER JOIN `teacher_student` ON (`teacher_grade`.`id` = `teacher_student`.`grade_id`) INNER JOIN `teacher_enroll` ON (`teacher_student`.`id` = `teacher_enroll`.`student_id`) INNER JOIN `teacher_course` ON (`teacher_enroll`.`course_id` = `teacher_course`.`id`) WHERE `teacher_course`.`name` LIKE BINARY %python%