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select_related()的作用
select_related()是Django ORM（对象关系映射）中的一种查询优化方法，主要用于减少数据库查询次数，提高查询效率。当你在查询一个模型实例时，如果这个实例有ForeignKey关联到其他模型，那么select_related()可以帮助你在一次数据库查询中同时获取到这些关联模型的数据。
1，创建应用
Test/app12
python manage.py startapp app12
2，注册应用
Test/Test/settings.py
3，添加应用路由
Test/Test/urls.py
from django.contrib import admin from django.urls import path, include urlpatterns = [ path('app12/', include('app12.urls')), ]
4，添加模型
Test/app12/models.py
# models.py from django.db import models class Author(models.Model): name = models.CharField(max_length=100) def __str__(self): return self.name class Post(models.Model): title = models.CharField(max_length=200) content = models.TextField() author = models.ForeignKey(Author, on_delete=models.CASCADE) def __str__(self): return self.title
5，添加视图函数
Test/app12/views.py
# views.py from django.shortcuts import render from .models import Post def post_list(request): posts = Post.objects.select_related('author').all() return render(request, '12/post_list.html', {'posts': posts})
6，添加html代码
Test/templates/12/post_list.html
<!-- post_list.html --> {% for post in posts %} <h2>{{ post.title }}</h2> <p>By: {{ post.author.name }}</p> <p>{{ post.content }}</p> {% endfor %}
7，添加路由地址
from django.urls import path from . import views urlpatterns = [ path('post_list/', views.post_list, name='post_list'), ]
8，添加数据
Test/add_data.py
import os import django import random from faker import Faker os.environ.setdefault("DJANGO_SETTINGS_MODULE", "Test.settings") django.setup() from app12.models import Author, Post fake = Faker() def add_data(): for _ in range(100): author = Author.objects.create(name=fake.name()) for _ in range(10): Post.objects.create( title=fake.sentence(), content=fake.text(), author=author ) if __name__ == '__main__': add_data()
9，访问页面
127.0.0.1:8000/app12/post_list/
