python - 如何拥有一个包含四个表的 Django 关系数据库？

Question

我正在使用 Django 创建网站，但数据库有问题!我有四个表(主题、问题、答案和图像)。这些表中的每一个都有一个 id 列，我想将这四个表连接在一起。

我尝试使用 ForeignKey() 但没有成功。我收到一条错误消息。我不知道在这种情况下是否可以使用 ManyToManyField()，因为我尝试连接的只是一列。

这是代码:

from django.db import models

# Create your models here.
class topics(models.Model):
    topic_id = models.AutoField(primary_key=True)
    topic_level = models.BooleanField()
    topic_name = models.TextField()

class questions(models.Model):
    question_id = models.AutoField(primary_key=True)
    description = models.TextField()
    questions_type = models.BooleanField()


class answers(models.Model):
    answer_id = models.AutoField(primary_key=True)
    description = models.TextField()

class images (models.Model):
    image_id = models.AutoField(primary_key=True)
    image_blob = models.BinaryField()

这是带有 ForeignKey() 的代码:

from django.db import models

# Create your models here.
class topics(models.Model):
    topic_id = models.AutoField(primary_key=True)
    topic_level = models.BooleanField()
    topic_name = models.TextField()
    topic_question = models.ForeignKey(questions, on_delete=CASCADE)
    topic_answer = models.ForeignKey(answers, on_delete=CASCADE)
    topic_image = models.ForeignKey(images, on_delete=CASCADE)


class questions(models.Model):
    question_id = models.AutoField(primary_key=True)
    description = models.TextField()
    questions_type = models.BooleanField()
    question_topic = models.ForeignKey(topics, on_delete=CASCADE)
    question_answer = models.ForeignKey(answers, on_delete=CASCADE)
    question_image = models.ForeignKey(images, on_delete=CASCADE)


class answers(models.Model):
    answer_id = models.AutoField(primary_key=True)
    description = models.TextField()
    answer_topic = models.ForeignKey(topics, on_delete=CASCADE)
    answer_question = models.ForeignKey(questions, on_delete=CASCADE)
    answer_image = models.ForeignKey(images, on_delete=CASCADE)

class images (models.Model):
    image_id = models.AutoField(primary_key=True)
    image_blob = models.BinaryField()
    image_topic = models.ForeignKey(topics, on_delete=CASCADE)
    image_question = models.ForeignKey(questions, on_delete=CASCADE)
    image_answer= models.ForeignKey(answers, on_delete=CASCADE)

这是我收到的错误消息:

topic_question = models.ForeignKey(questions, on_delete=CASCADE) NameError: name 'questions' is not defined

Answer 1

当您尝试使用question类名称来指示相关模型时，此类未定义，如错误所示。当您引用稍后在代码中定义的模型时，您必须将名称括在 "" 中:

topic_question = models.ForeignKey("questions", on_delete=CASCADE)

以下是相关文档:https://docs.djangoproject.com/en/dev/ref/models/fields/#django.db.models.ForeignKey