在 Django 中进行无重复外键引用的设计
我想创建一个费用跟踪应用程序，每个用户都可以在其中输入费用并将其分类为自己的类别。这是我使用的模型定义：
from django.db import models
from django.contrib.auth.models import User
class Category(models.Model):
user = models.ForeignKey(User, related_name="my_categories")
name = models.CharField(max_length=50)
class Expense(models.Model):
date = models.DateField()
amount = models.IntegerField()
description = models.TextField()
category = models.ForeignKey(Category)
user = models.ForeignKey(User)
每个类别都必须与一个用户关联，以便我们可以在输入费用时向每个用户显示他自己的类别以供选择。出于类似的原因，每个费用记录都应该与一个用户相关联。但在费用的定义中，我们有两个对用户模型的引用，一个直接通过“用户”字段，另一个通过具有用户引用的“类别”字段。
我认为像这样的多次引用是一件坏事。有更好的方法来建模吗？我知道我们可以从类别参考中找出用户，但这似乎是一种迂回的方法。
I want to create an expense tracking application, where each user can enter expenses and classify them into his own categories. Here is the model definition that I use:
from django.db import models
from django.contrib.auth.models import User
class Category(models.Model):
user = models.ForeignKey(User, related_name="my_categories")
name = models.CharField(max_length=50)
class Expense(models.Model):
date = models.DateField()
amount = models.IntegerField()
description = models.TextField()
category = models.ForeignKey(Category)
user = models.ForeignKey(User)
Each category will have to be associated with a user so that we can display each user his own categories to choose while entering the expense. For similar reasons, each expense record should be associated with a user. But in definition of Expense, we are having 2 references to the User models, one directly through 'user' field and another through the 'category' field which has a user reference.
I believe that multiple references like this is a bad thing. Is there a better way to model this? I understand that we can find out the user from the category reference, but it seems a roundabout way of doing it.
如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（1）
尽管您的数据库不是 100% 标准化，但就您而言，我不认为第二个参考是多余的。 “费用”和“类别”都是定义明确的实体，属于用户。如果您稍后想要更改外键以允许空类别或ManyToManyField，您将立即注意到这两个用户字段都是必需的。当该列存在时，用户的查找对于数据库和开发人员来说也更加容易。
Although your db is not 100% normalized, in your case, I do not believe the second reference is redundant. Both 'an expense' and 'a category' are well defined entities, which belong to a user. If you will later want to change your foreign key to allow a null category or to a ManyToManyField, you will notice immediatly that both user fields are required. Lookups by user are also much easier for the db and developer when the column is there.