一对多外键增删改查

# 一对多外键增删改查
    # 增
    # 1  直接写实际字段 id
    # models.Book.objects.create(title='论语',price=899.23,publish_id=1)
    # models.Book.objects.create(title='聊斋',price=444.23,publish_id=2)
    # models.Book.objects.create(title='老子',price=333.66,publish_id=1)
    # 2  虚拟字段 对象
    # publish_obj = models.Publish.objects.filter(pk=2).first()
    # models.Book.objects.create(title='红楼梦',price=666.23,publish=publish_obj)

    # 删
    # models.Publish.objects.filter(pk=1).delete()  # 级联删除

    # 修改
    # models.Book.objects.filter(pk=1).update(publish_id=2)
    # publish_obj = models.Publish.objects.filter(pk=1).first()
    # models.Book.objects.filter(pk=1).update(publish=publish_obj)