class A(model.Model):
    ...
class B(model.Model):
    屬性 = models.OneToOneField(A, on_delete=xxx)

# file : xxxxxxxx/models.py
from django.db import models

class Author(models.Model):
? ? '''作家模型類'''
? ? name = models.CharField('作家', max_length=50)

class Wife(models.Model):
? ? '''作家妻子模型類'''
? ? name = models.CharField("妻子", max_length=50)
? ? author = models.OneToOneField(Author, on_delete=models.CASCADE) ?# 增加一對一屬性?

from .models import *
author1 = Author.objects.create(name='王老師')
wife1 = Wife.objects.create(name='王夫人', author=author1)  # 關(guān)聯(lián)王老師
author2 = Author.objects.create(name='小澤老師')  # 一對一可以沒有數(shù)據(jù)對應(yīng)的數(shù)據(jù) 

# 通過 wife 找 author
from .models import Wife
wife = Wife.objects.get(name='王夫人')
print(wife.name, '的老公是', wife.author.name)

# 通過 author.wife 關(guān)聯(lián)屬性 找 wife,如果沒有對應(yīng)的wife則觸發(fā)異常
author1 = Author.objects.get(name='王老師')
print(author1.name, '的妻子是', author1.wife.name)
author2 = Author.objects.get(name='小澤老師')
try:
    print(author2.name, '的妻子是', author2.wife.name)
except:
    print(author2.name, '還沒有妻子')

class A(model.Model):
? ? ...

class B(model.Model):
? ? 屬性 = models.ForeignKey("一"的模型類, on_delete=xx)

# file: otm/models.py
from django.db import models

class Publisher(models.Model):
?? ?'''出版社【一】'''
? ? name = models.CharField('名稱', max_length=50, unique=True)

class Book(models.Model):
? ? '''書【多】'''
? ? title = models.CharField('書名', max_length=50)
? ? publisher = ForeignKey(Publisher, on_delete=models.CASCADE)

#先創(chuàng)建 '一' ，再創(chuàng)建 '多'
from .models import *
pub1 = Publisher.objects.create(name='清華大學出版社')
Book.objects.create(title='C++', publisher=pub1)
Book.objects.create(title='Java', publisher_id=1)

#高級創(chuàng)建 - 利用 反向?qū)傩?
pub2 = Publisher.objects.create(name='北京大學出版社')
pub2.book_set.create(title='西游記')

通過 publisher 屬性查詢即可
???????book.publisher
 
abook = Book.objects.get(id=1)
print(abook.title, '的出版社是:', abook.publisher.name)

# 通過出版社查詢對應(yīng)的書
pub1 = Publisher.objects.get(name='清華大學出版社')
books = pub1.book_set.all()  # 通過book_set 獲取pub1對應(yīng)的多個Book數(shù)據(jù)對象
#books = Book.objects.filter(publisher=pub1)  # 也可以采用此方式獲取
print("清華大學出版社的書有:")
for book in books:
   print(book.title)

屬性 = models.ManyToManyField(MyModel)

class Author(models.Model):
? ? ...

class Book(models.Model):
? ? ...
? ? authors = models.ManyToManyField(Author)

class Author(models.Model):
    '''作家模型類'''
    name = models.CharField('作家', max_length=50)
    def __str__(self):
        return self.name
    
class Book(models.Model):
    '''書模型類'''
    title = models.CharField('書名', max_length=50)
    authors = models.ManyToManyField(Author)
    def __str__(self):
           return self.title 

方案1 先創(chuàng)建 author 再關(guān)聯(lián) book
    author1 = Author.objects.create(name='呂老師')
    author2 = Author.objects.create(name='王老師')
    # 呂老師和王老師同時寫了一本Python
    book11 = author1.book_set.create(title="Python")
    author2.book_set.add(book11) 
    
方案2 先創(chuàng)建 book 再關(guān)聯(lián) author
    book = Book.objects.create(title='python1')
    #郭小鬧和呂老師都參與了 python1 的 創(chuàng)作
    author3 = book.authors.create(name='guoxiaonao')
    book.authors.add(author1)

author.book_set.all()
author.book_set.filter()