如何擁有一個帶有四個表的 Django 關系數據庫？

Question

我正在使用 Django 創建一個網站，但數據庫有問題！ 我有四個表（主題、問題、答案和圖像）。 這些表中的每一個都有一個 id 列，我想將這四個表連接在一起。

我曾嘗試使用ForeignKey()但沒有成功。 我收到一條錯誤消息。 我不知道在這種情況下我是否可以使用ManyToManyField() ，因為它只是我試圖連接的一列。

這是代碼：

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()

這是帶有ForeignKey()的代碼：

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)

這是我收到的錯誤消息：

topic_question = models.ForeignKey(questions, on_delete=CASCADE) NameError: name 'questions' 未定義

Answer 1

在您嘗試使用question類名稱來指示相關模型時，未定義此類類，如錯誤所述。 當您引用稍后在代碼中定義的模型時，您必須將名稱括在"" ：

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

這是相關文檔： https : //docs.djangoproject.com/en/dev/ref/models/fields/#django.db.models.ForeignKey