Django 外键的操作

from django.db import models


class Publisher(models.Model):
    name = models.CharField(max_length=32, verbose_name='出版社名称')

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = "name"
        verbose_name_plural = verbose_name


class Book(models.Model):
    name = models.CharField(max_length=32, verbose_name='书名')
    pub = models.ForeignKey('Publisher', on_delete=models.CASCADE,related_name='books', related_query_name='book')

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = 'name'
        verbose_name_plural = verbose_name

########################
# 基于对象的查询
book_obj = models.Book.objects.get(pk=1)
# 正向查询
book_obj.pub    # 所关联的对象
book_obj.pub_id # 所关联的对象id
# 反向查询
pub_obj = models.Publisher.objects.get(pk=1)

# 不指定related_name 使用 类名下列_set
pub_obj.book_set    # 关系管理对象
pub_obj.book_set.all()  # 所关联的所有的书籍对象

# 指定 related_name = 'books'
pub_obj.books.all()

# 基于字段的查询
ret = models.Book.objects.filter(name='xxxxxxxx')
ret = models.Book.objects.filter(pub__name='出版社')

ret = models.Publisher.objects.filter(name='出版社')

# 不指定 related_name
ret = models.Publisher.objects.filter(book__name='xxxxxxx')
# 指定 related_name='books'
ret = models.Publisher.objects.filter(books__name='xxxxxxx')
# 指定related_query_name='xxx'
ret = models.Publisher.objects.filter(xxx__name='xxxxx')