Django 模型 - 选择与外键

Django是一个流行的Python Web框架，它提供了一种简单而高效的方式来开发Web应用程序。在Django中，模型是用于定义数据结构的关键组成部分。在某些情况下，我们可能需要在模型中使用外键来建立关联关系。本文将介绍在Django模型中选择与外键的使用方法，并提供相关的案例代码。

python
from django.db import models
class User(models.Model):
    name = models.CharField(max_length=100)
class Order(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    product = models.CharField(max_length=100)
    quantity = models.IntegerField()

python
class Product(models.Model):
    name = models.CharField(max_length=100)
class Order(models.Model):
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    quantity = models.IntegerField()
    SIZE_CHOICES = [
        ('S', 'Small'),
        ('M', 'Medium'),
        ('L', 'Large'),
    ]
    size = models.CharField(max_length=1, choices=SIZE_CHOICES)

python
class Category(models.Model):
    name = models.CharField(max_length=100)
class Product(models.Model):
    name = models.CharField(max_length=100)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
class Order(models.Model):
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    quantity = models.IntegerField()
    size = models.CharField(max_length=1, choices=[('S', 'Small'), ('M', 'Medium'), ('L', 'Large')])