关于Django多应用模型存储及跨应用表关联的技术咨询

Hey there! Let's start by clearing up a tiny wording tweak first: each Python class you define in models.py represents a database table, not a "Python table"—that's just a minor terminology fix, no big deal! 😊

To answer your questions directly:

1. 所有应用的模型表默认存在同一个数据库吗？ #

Absolutely yes! By default, Django uses a single database configured in your project's settings.py (under the DATABASES setting). Every model from every app in your project will create its corresponding table in this database.

You'll notice the table names follow a pattern: [app_name]_[model_name] (e.g., if you have an app named blog with a Post model, the table will be blog_post; an app named shop with a Product model becomes shop_product). This prevents naming conflicts between models from different apps.

If you ever need to split tables across multiple databases, Django does support database routing, but that's an advanced use case—most beginner projects won't need this.

2. 能跨应用关联/查询不同表的数据吗？ #

100% possible, and it's actually a common practice in Django! You can create relationships between models from different apps using Django's standard relational fields (ForeignKey, OneToOneField, ManyToManyField), and perform joins in your queries seamlessly.

Example: Cross-app model relationship #

Suppose you have a blog app with a Post model, and a shop app where you want to link products to related blog posts:

# shop/models.py
from django.db import models
# Import the model from the other app
from blog.models import Post

class Product(models.Model):
    name = models.CharField(max_length=100)
    price = models.DecimalField(max_digits=10, decimal_places=2)
    # Create a foreign key to the Post model from the blog app
    related_blog_post = models.ForeignKey(
        Post,
        on_delete=models.CASCADE,
        null=True,
        blank=True
    )

Example: Cross-app query (joining data) #

Once the relationship is set up, you can query across apps just like you would with models in the same app:

# Get a product and access its related blog post
from shop.models import Product
product = Product.objects.get(id=1)
print(product.related_blog_post.title)

# Get all blog posts that have at least one related product
from blog.models import Post
posts_with_products = Post.objects.filter(product__isnull=False)

Don't worry about feeling like you're copying code without understanding it—Django's official tutorial is focused on getting you up and running quickly, so it skips some of these "under the hood" details. Asking these questions is exactly how you'll build a solid understanding of how Django works!

备注：内容来源于stack exchange，提问作者Emi Buliga