一：“一對多”模型關系

? 在“多”方模型類創建外鍵類屬性，關聯“一”方。

class School(models.Model): # "一"方模型 pass

class Student(models.Model): # "多"方模型 stuschool = models.ForeignKey(School,on_delete=models.CASCADE)

1.創建“一”方模型對象

school1 = School.objects.create(name="清華大學",address="北京",establish_date=date(1901,4,10))

2.創建“多”方模型對象

方式一：通過“一”方的實例化對象關聯stu1 = Student.objects.create(name="張清華",sex='男',score=83.5,stuschool=school1)

方式二：通過對應表的外鍵關聯stu2 = Student.objects.create(name="李清華",sex="女",score=89,stuschool_id=1)

方式三：通過“一”方添加對象stu3 = school1.student_set.create(name="趙清華",sex='女',score=93)

3.從“一”方查詢“多”方

使用“多”方模型類小寫_set，作為“一”方容器。students = school1.student_set.all()

4.從“多”方查詢“一”方

使用“多”方外鍵屬性直接獲取對應的“一”方實例school = stu1.stuschool

5.代碼演示

1、models

from django.db import models ? ? class School(models.Model):name = models.CharField(max_length=20)address = models.CharField(max_length=30)establish_date = models.DateField() ?def __str__(self):return self.name ?class Meta:db_table = 'schools'ordering = ('establish_date',) ? class Student(models.Model):name = models.CharField(max_length=20)sex = models.CharField(max_length=10)score = models.FloatField()stuschool = models.ForeignKey(School,on_delete=models.CASCADE) ?def __str__(self):return self.name ?class Meta:db_table = 'students'ordering = ('-score','-id') ?

2、Terminal

? C:\python\DjangoDay41>python manage.py startapp one2ma ngapp ? C:\python\DjangoDay41>python manage.py makemigrations Migrations for 'one2mangapp':one2mangapp\migrations\0001_initial.py- Create model School- Create model Student ? C:\python\DjangoDay41>python manage.py migrate Operations to perform:Apply all migrations: admin, auth, contenttypes, hom ework, one2mangapp, sessions Running migrations:Applying one2mangapp.0001_initial... OK ? C:\python\DjangoDay41>python manage.py shell Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51 ) [MSC v.1914 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for m ore information. (InteractiveConsole) ? >>> from one2mangapp.models import * ? >>> from datetime import date ? >>> school1 = School.objects.create(name="清華大學",address="北京",establish_date=date(1901,4,10)) >>> stu1 = Student.objects.create(name="張清華",sex='男',score=83.5,stuschool=school1) >>> stu2 = Student.objects.create(name="李清華",sex="女",score=89,stuschool_id=1) >>> stu3 = school1.student_set.create(name="趙清華",sex='女 ',score=93) >>> stu4 = school1.student_set.create(name="王清華",sex='女 ',score=85) >>> school2 = School.objects.create(name="北京大學",address ="北京",establish_date=date(1903,3,15)) >>> schools = School.objects.all() >>> for s in schools: ... ? ? print(s) ... 清華大學 北京大學 >>> students = Student.objects.all() >>> for s in students: ... ? ? print(s) ... 趙清華 李清華 王清華 張清華 >>> schools = School.objects.all() >>> for s in schools: ... ? ? print(s) ... 清華大學 北京大學 ? >>> students = Student.objects.all() >>> for s in schools: ... ? ? print(s) ... 清華大學 北京大學 >>> for s in students: ... ? ? print(s) ... 趙清華 李清華 王清華 張清華 >>> school1 = School.objects.get(id=1) >>> school1 <School: 清華大學> >>> students = school1.student_set.all() >>> for s in students: ... ? ? print(s) ... 趙清華 李清華 王清華 張清華 >>> school2 = Student.objects.get(id=2) >>> school2 <Student: 李清華> >>> school2 = School.objects.get(id=2) >>> school2 <School: 北京大學> ? >>> Student.objects.create(name='劉備大',sex='男',score=88, stuschool=school2) <Student: 劉備大> >>> Student.objects.create(name='王備大',sex='男',score=88, stuschool=school2) <Student: 王備大> >>> students = school2.student_set.all() >>> for s in students: ... ? ? print(s) ... 王備大 劉備大 >>> stu1 = Student.objects.get(id=5) >>> stu1 <Student: 劉備大> >>> stu1.stuschool <School: 北京大學> ?

?

二：“一對一”模型關系

? 在維護關系的“一方”使用models.OneToOneField(“另一個一方模型類名稱”,on_delete=models.CASCADE) class Person(models.Model): pass

class IDCard(models.Model): cardno = models.CharField(max_length=20,primary_key=True) per = models.OneToOneField(Person,on_delete=models.CASCADE) # 一對一關聯

1.創建不負責維護關系的“一方”

per1 = Person.objects.create(name="張三",age=20,ismarried=False)

2.創建負責維護關系的“一方”

方式一：通過另一方的實例化對象關聯card1 = IDCard.objects.create(cardno='zs123456',per=per1)

方式二：通過表中的唯一外鍵關聯card2 = IDCard.objects.create(cardno='ls123456',per_id=2)

3.從“主動一方”查詢“被動一方”

通過“被動一方”模型類名的小寫形式card1 = per1.idcard

4.從“被動一方”查詢“主動一方”

通過“被動一方”的維護關系的類屬性直接查詢到“主動一方”per1 = card1.per

5.刪除記錄

per = Person.objects.get(id=2) # 查詢2號記錄per.delete() # 刪除2號記錄（級聯刪除）

6.代碼演示

1、models

from django.db import models ? class Person(models.Model):name = models.CharField(max_length=10)age = models.IntegerField()ismarried = models.BooleanField() ?def __str__(self):return self.name ?class Meta:db_table = 'person' ? ? class IDCard(models.Model):cardno = models.CharField(max_length=20,primary_key=True)per = models.OneToOneField(Person,on_delete=models.CASCADE) # 一對一關聯 ?def __str__(self):return self.cardno ?class Meta:db_table = 'cards'

2、Terminal

C:\python\DjangoDay41>python manage.py startapp one2oneapp ? C:\python\DjangoDay41>python manage.py makemigrations Migrations for 'one2oneapp':one2oneapp\migrations\0001_initial.py- Create model IDCard- Create model Person- Add field per to idcard ? C:\python\DjangoDay41>python manage.py migrate Operations to perform:Apply all migrations: admin, auth, contenttypes, homework , one2mangapp, one2oneapp, sessions Running migrations:Applying one2oneapp.0001_initial... OK ? C:\python\DjangoDay41>python manage.py shell Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MS C v.1914 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more i nformation. (InteractiveConsole) >>> from one2oneapp.models import * >>> per1 = Person.objects.create(name="張三",age=20,ismarri ed=False) >>> per1 = Person.objects.create(name="李娟",age=20,ismarri ed=True) ?

三：“多對多”關系

? 在某個“多方”通過 models.ManyToManyField(另一個多方模型類,through="中間關系模型類") 設置模型之間的關系。

在中間模型類中至少有兩個外鍵類屬性，分別關聯兩個多方模型。

class Student(models.Model): pass

class Course(models.Model): name = models.CharField(max_length=10) stu = models.ManyToManyField(Student,through="Student_Course") # 多對多關系

class Student_Course(models.Model): # 中間模型，負責維護兩個“多方”模型 student = models.ForeignKey(Student,on_delete=models.CASCADE) # 關聯Student模型的外鍵 course = models.ForeignKey(Course,on_delete=models.CASCADE) # 關聯Course模型的外鍵 score = models.FloatField()

1.添加不負責維護關系的“多方”

stu1 = Student.objects.create(name="張三",age=20,sex='男')

2.創建負責關聯的“多方”

course1 = Course.objects.create(name='數學')

3.創建第三方關系

使用實例化對象關聯sc1 = Student_Course.objects.create(student=stu1,course=course1,score=85)

使用外鍵值關聯sc3 = Student_Course.objects.create(student_id=3,course_id=1,score=69)

4.從不負責的多方查詢另一個多方

例如：1號學生選的課程 student1 = Student.objects.get(id=1) courses = student1.course_set.all() # 對方模型類小寫_set

5.從負責關聯的多方查詢另一個多方

例如：查詢選擇2號課程的學生course2 = Course.objects.get(id=2)students = course2.stu.all() # stu為關聯類屬性

? ??6.代碼演示

1、models

from django.db import models ? class Student(models.Model):name = models.CharField(max_length=10)age = models.IntegerField()sex = models.CharField(max_length=10) ?def __str__(self):return self.name ?class Meta:db_table = 'many_students' ? class Course(models.Model):name = models.CharField(max_length=10)stu = models.ManyToManyField(Student,through="Student_Course") # 多對多關系 ?def __str__(self):return self.name ?class Meta:db_table = 'courses' ? class Student_Course(models.Model): ? # 中間模型，負責維護兩個“多方”模型student = models.ForeignKey(Student,on_delete=models.CASCADE) ?# 關聯Student模型的外鍵course = models.ForeignKey(Course,on_delete=models.CASCADE) # 關聯Course模型的外鍵score = models.FloatField() ?class Meta:db_table = 'student_course' ?

? 2、MySQL

ywh@ubuntu:~$ mysql -u root -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.7.23-0ubuntu0.16.04.1 (Ubuntu) ? Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved. ? Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. ? Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. ? mysql> use mydb Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A ? Database changed mysql> show tables; +----------------------------+ | Tables_in_mydb ? ? ? ? ? ? | +----------------------------+ | articles ? ? ? ? ? ? ? ? ? | | auth_group ? ? ? ? ? ? ? ? | | auth_group_permissions ? ? | | auth_permission ? ? ? ? ? | | auth_user ? ? ? ? ? ? ? ? | | auth_user_groups ? ? ? ? ? | | auth_user_user_permissions | | cakes ? ? ? ? ? ? ? ? ? ? | | cards ? ? ? ? ? ? ? ? ? ? | | django_admin_log ? ? ? ? ? | | django_content_type ? ? ? | | django_migrations ? ? ? ? | | django_session ? ? ? ? ? ? | | myapp_product ? ? ? ? ? ? | | person ? ? ? ? ? ? ? ? ? ? | | schools ? ? ? ? ? ? ? ? ? | | students ? ? ? ? ? ? ? ? ? | | workers ? ? ? ? ? ? ? ? ? | +----------------------------+ 18 rows in set (0.00 sec) ? mysql> show tables; +----------------------------+ | Tables_in_mydb ? ? ? ? ? ? | +----------------------------+ | articles ? ? ? ? ? ? ? ? ? | | auth_group ? ? ? ? ? ? ? ? | | auth_group_permissions ? ? | | auth_permission ? ? ? ? ? | | auth_user ? ? ? ? ? ? ? ? | | auth_user_groups ? ? ? ? ? | | auth_user_user_permissions | | cakes ? ? ? ? ? ? ? ? ? ? | | cards ? ? ? ? ? ? ? ? ? ? | | courses ? ? ? ? ? ? ? ? ? | | django_admin_log ? ? ? ? ? | | django_content_type ? ? ? | | django_migrations ? ? ? ? | | django_session ? ? ? ? ? ? | | many_students ? ? ? ? ? ? | | myapp_product ? ? ? ? ? ? | | person ? ? ? ? ? ? ? ? ? ? | | schools ? ? ? ? ? ? ? ? ? | | student_course ? ? ? ? ? ? | | students ? ? ? ? ? ? ? ? ? | | workers ? ? ? ? ? ? ? ? ? | +----------------------------+ 21 rows in set (0.00 sec) ? mysql> desc student_course; +------------+---------+------+-----+---------+----------------+ | Field ? ? | Type ? | Null | Key | Default | Extra ? ? ? ? | +------------+---------+------+-----+---------+----------------+ | id ? ? ? ? | int(11) | NO ? | PRI | NULL ? | auto_increment | | score ? ? | double | NO ? | ? ? | NULL ? | ? ? ? ? ? ? ? | | course_id | int(11) | NO ? | MUL | NULL ? | ? ? ? ? ? ? ? | | student_id | int(11) | NO ? | MUL | NULL ? | ? ? ? ? ? ? ? | +------------+---------+------+-----+---------+----------------+ 4 rows in set (0.01 sec) ? mysql> show creat table student_course; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that nds to your MySQL server version for the right syntax to use near 'creat table sourse' at line 1 mysql> show create table student_course; +----------------+------------------------------------------- | Table ? ? ? ? | Create Table ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? | student_course | CREATE TABLE `student_course` (`id` int(11) NOT NULL AUTO_INCREMENT,`score` double NOT NULL,`course_id` int(11) NOT NULL,`student_id` int(11) NOT NULL,PRIMARY KEY (`id`),KEY `student_course_course_id_16fdadee_fk_courses_id` (`course_id`),KEY `student_course_student_id_b55d2772_fk_many_students_id` (`student_id`),CONSTRAINT `student_course_course_id_16fdadee_fk_courses_id` FOREIGN KEY (`cou REFERENCES `courses` (`id`),CONSTRAINT `student_course_student_id_b55d2772_fk_many_students_id` FOREIGN KEent_id`) REFERENCES `many_students` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 | +----------------+------------------------------------------- 1 row in set (0.01 sec) ? mysql> select * from django_migrations; +----+--------------+------------------------------------------+--------------------+ | id | app ? ? ? ? | name ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? | applied ? ? ? ? ? | +----+--------------+------------------------------------------+--------------------+ | ?1 | contenttypes | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-07 09:0333 | | ?2 | auth ? ? ? ? | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-07 09:0574 | | ?3 | admin ? ? ? | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-07 09:0514 | | ?4 | admin ? ? ? | 0002_logentry_remove_auto_add ? ? ? ? ? | 2018-10-07 09:0510 | | ?5 | admin ? ? ? | 0003_logentry_add_action_flag_choices ? | 2018-10-07 09:0498 | | ?6 | contenttypes | 0002_remove_content_type_name ? ? ? ? ? | 2018-10-07 09:0023 | | ?7 | auth ? ? ? ? | 0002_alter_permission_name_max_length ? | 2018-10-07 09:0994 | | ?8 | auth ? ? ? ? | 0003_alter_user_email_max_length ? ? ? ? | 2018-10-07 09:0963 | | ?9 | auth ? ? ? ? | 0004_alter_user_username_opts ? ? ? ? ? | 2018-10-07 09:0950 | | 10 | auth ? ? ? ? | 0005_alter_user_last_login_null ? ? ? ? | 2018-10-07 09:0923 | | 11 | auth ? ? ? ? | 0006_require_contenttypes_0002 ? ? ? ? ? | 2018-10-07 09:0917 | | 12 | auth ? ? ? ? | 0007_alter_validators_add_error_messages | 2018-10-07 09:0910 | | 13 | auth ? ? ? ? | 0008_alter_user_username_max_length ? ? | 2018-10-07 09:0883 | | 14 | auth ? ? ? ? | 0009_alter_user_last_name_max_length ? ? | 2018-10-07 09:0827 | | 15 | myapp ? ? ? | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-07 09:0813 | | 16 | sessions ? ? | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-07 09:0789 | | 17 | myapp ? ? ? | 0002_article ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-08 02:4833 | | 18 | managerapp ? | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-09 06:2514 | | 19 | homework ? ? | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-10 01:1268 | | 20 | one2mangapp | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-10 04:4523 | | 21 | one2oneapp ? | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-11 14:0905 | | 22 | many2manyapp | 0001_initial ? ? ? ? ? ? ? ? ? ? ? ? ? ? | 2018-10-26 01:1869 | +----+--------------+------------------------------------------+--------------------+ 22 rows in set (0.00 sec) ? mysql> select * from many_students; +----+--------+-----+-----+ | id | name ? | age | sex | +----+--------+-----+-----+ | ?1 | 張三 ? | ?20 | 男 | | ?2 | 李四 ? | ?22 | 男 | | ?3 | 李四 ? | ?22 | 男 | | ?4 | 王五 ? | ?26 | 男 | +----+--------+-----+-----+ 4 rows in set (0.01 sec) ? mysql> select * from courses; +----+--------+ | id | name ? | +----+--------+ | ?1 | 數學 ? | | ?2 | 英語 ? | | ?3 | python | +----+--------+ 3 rows in set (0.02 sec) mysql> select * from student_course; +----+-------+-----------+------------+ | id | score | course_id | student_id | +----+-------+-----------+------------+ | ?1 | ? ?85 | ? ? ? ? 1 | ? ? ? ? ?1 | | ?3 | ? ?95 | ? ? ? ? 3 | ? ? ? ? ?2 | | ?4 | ? ?90 | ? ? ? ? 3 | ? ? ? ? ?4 | | ?5 | ? ?80 | ? ? ? ? 2 | ? ? ? ? ?3 | +----+-------+-----------+------------+ 4 rows in set (0.00 sec) ? mysql> select * from student_course; +----+-------+-----------+------------+ | id | score | course_id | student_id | +----+-------+-----------+------------+ | ?1 | ? ?85 | ? ? ? ? 1 | ? ? ? ? ?1 | | ?3 | ? ?95 | ? ? ? ? 3 | ? ? ? ? ?2 | | ?4 | ? ?90 | ? ? ? ? 3 | ? ? ? ? ?4 | | ?5 | ? ?80 | ? ? ? ? 2 | ? ? ? ? ?3 | | ?6 | ? ?75 | ? ? ? ? 2 | ? ? ? ? ?2 | +----+-------+-----------+------------+ 5 rows in set (0.00 sec) ? mysql> select * from many_students; +----+--------+-----+-----+ | id | name ? | age | sex | +----+--------+-----+-----+ | ?1 | 張三 ? | ?20 | 男 | | ?2 | 李四 ? | ?22 | 男 | | ?3 | 李四 ? | ?22 | 男 | | ?4 | 王五 ? | ?26 | 男 | +----+--------+-----+-----+ 4 rows in set (0.00 sec) ? mysql> select * from many_students; +----+--------+-----+-----+ | id | name ? | age | sex | +----+--------+-----+-----+ | ?1 | 張三 ? | ?20 | 男 | | ?3 | 李四 ? | ?22 | 男 | | ?4 | 王五 ? | ?26 | 男 | +----+--------+-----+-----+ 3 rows in set (0.01 sec) ? mysql> select * from student_course; +----+-------+-----------+------------+ | id | score | course_id | student_id | +----+-------+-----------+------------+ | ?1 | ? ?85 | ? ? ? ? 1 | ? ? ? ? ?1 | | ?4 | ? ?90 | ? ? ? ? 3 | ? ? ? ? ?4 | | ?5 | ? ?80 | ? ? ? ? 2 | ? ? ? ? ?3 | +----+-------+-----------+------------+ 3 rows in set (0.00 sec) ? mysql> select * from courses; +----+--------+ | id | name ? | +----+--------+ | ?1 | 數學 ? | | ?2 | 英語 ? | | ?3 | python | +----+--------+ 3 rows in set (0.00 sec) ? mysql> select * from courses; +----+--------+ | id | name ? | +----+--------+ | ?1 | 數學 ? | | ?2 | 英語 ? | +----+--------+ 2 rows in set (0.00 sec)

3、Terminal

Microsoft Windows [版本 10.0.17763.55] (c) 2018 Microsoft Corporation。保留所有權利。pytho ? C:\python\DjangoDay41>python manage.py makemigrations Migrations for 'many2manyapp':many2manyapp\migrations\0001_initial.py- Create model Course- Create model Student- Create model Student_Course- Add field stu to course ? C:\python\DjangoDay41>python manage.py migrate Operations to perform:Apply all migrations: admin, auth, contenttypes, hom ework, many2manyapp, one2mangapp, one2oneapp, sessions ? Running migrations:Applying many2manyapp.0001_initial... OK ? C:\python\DjangoDay41>python manage.py shell Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51 ) [MSC v.1914 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for m ore information. (InteractiveConsole) >>> from many2manyapp.models import * >>> >>> stu1 = Student.objects.create(name="張三",age=20,s ex='男') >>> course1 = Course.objects.create(name='數學') >>> sc1 = Student_Course.objects.create(student=stu1,c ourse=course1,score=85) ? >>> stu1 = Student.objects.create(name="李四",age=22,s ex='男') >>> stu2 = Student.objects.create(name="李四",age=22,s ex='男') >>> stu3 = Student.objects.create(name="王五",age=26,s ex='男') >>> course2 = Course.objects.create(name='英語') >>> course3 = Course.objects.create(name='python') >>> sc2 = Student_Course.objects.create(student=stu1,c ourse=course3,score=95) >>> sc3 = Student_Course.objects.create(student=stu3,c ourse=course3,score=90) >>> sc3 = Student_Course.objects.create(student=stu2,c ourse=course2,score=80) >>> sc2 = Student_Course.objects.create(student=stu1,c ourse=course2,score=75) >>> student1 = Student.objects.get(id=1) >>> student1 = Student.objects.get(id=2) >>> courses = student1.course_set.all() >>> for course in courses: ... ? ? print(course) ... 英語 python >>> student1 = Student.objects.get(id=3) >>> courses = student1.course_set.all() >>> for course in courses: ... ? ? print(course) ... 英語 >>> >>> course2 = Course.objects.get(id=2) >>> students = course2.stu.all() >>> for i in students: ... ? ? print(i.name) ... 李四 李四 >>> students = course3.stu.all() >>> for i in students: ... ? ? print(i.name) ... 李四 王五 ? >>> student1 = Student.objects.get(id=2) >>> student1.delete() (3, {'many2manyapp.Student_Course': 2, 'many2manyapp.S tudent': 1}) >>> course = Course.objects.get(id=3) >>> course.delete() (2, {'many2manyapp.Student_Course': 1, 'many2manyapp.C ourse': 1})

?

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