ORM初级实战简单的数据库交互

setting.py中：

 """
 Django settings for untitled3 project.

 Generated by 'django-admin startproject' using Django 2.0.7.

 For more information on this file, see
 https://docs.djangoproject.com/en/2.0/topics/settings/

 For the full list of settings and their values, see
 https://docs.djangoproject.com/en/2.0/ref/settings/
 """

 import os

 # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))

 # Quick-start development settings - unsuitable for production
 # See https://docs.djangoproject.com/en/2.0/howto/deployment/checklist/

 # SECURITY WARNING: keep the secret key used in production secret!
 SECRET_KEY = '3p4)ob=u_tpk_ha+5fs1x8vfn+(s5-92$(05%r04ny9v+dv=qp'

 # SECURITY WARNING: don't run with debug turned on in production!
 DEBUG = True

 ALLOWED_HOSTS = []

 # Application definition

 INSTALLED_APPS = [
     'django.contrib.admin',
     'django.contrib.auth',
     'django.contrib.contenttypes',
     'django.contrib.sessions',
     'django.contrib.messages',
     'django.contrib.staticfiles',
     'app01',
 ]

 MIDDLEWARE = [
     'django.middleware.security.SecurityMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.middleware.common.CommonMiddleware',
     #'django.middleware.csrf.CsrfViewMiddleware',
     'django.contrib.auth.middleware.AuthenticationMiddleware',
     'django.contrib.messages.middleware.MessageMiddleware',
     'django.middleware.clickjacking.XFrameOptionsMiddleware',
 ]

 ROOT_URLCONF = 'untitled3.urls'

 TEMPLATES = [
     {
         'BACKEND': 'django.template.backends.django.DjangoTemplates',
         'DIRS': [os.path.join(BASE_DIR, 'templates')]
         ,
         'APP_DIRS': True,
         'OPTIONS': {
             'context_processors': [
                 'django.template.context_processors.debug',
                 'django.template.context_processors.request',
                 'django.contrib.auth.context_processors.auth',
                 'django.contrib.messages.context_processors.messages',
             ],
         },
     },
 ]

 WSGI_APPLICATION = 'untitled3.wsgi.application'

 # Database
 # https://docs.djangoproject.com/en/2.0/ref/settings/#databases

 DATABASES = {
     'default': {
         'ENGINE': 'django.db.backends.sqlite3',
         'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
     }
 }

 # Password validation
 # https://docs.djangoproject.com/en/2.0/ref/settings/#auth-password-validators

 AUTH_PASSWORD_VALIDATORS = [
     {
         'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
     },
     {
         'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
     },
     {
         'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
     },
     {
         'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
     },
 ]

 # Internationalization
 # https://docs.djangoproject.com/en/2.0/topics/i18n/

 LANGUAGE_CODE = 'en-us'

 TIME_ZONE = 'UTC'

 USE_I18N = True

 USE_L10N = True

 USE_TZ = True

 # Static files (CSS, JavaScript, Images)
 # https://docs.djangoproject.com/en/2.0/howto/static-files/

 STATIC_URL = '/static/'

models.py中（数据库创建表结构都在这里）：

 from django.db import models

 # Create your models here.
 class Business(models.Model):
     caption = models.CharField(max_length=32)
     code = models.CharField(max_length=32,null=True,default='SA')#default是设置默认值，null=True是数据库中允许这个字段为空

 class Host(models.Model):
     nid = models.AutoField(primary_key=True) #设置主键并自增

     hostname = models.CharField(max_length=32,db_index=True)#max_length设置字段最大长度

     ip = models.GenericIPAddressField(protocol='ipv4',db_index=True)#db_index=True设置为索引

     port = models.IntegerField()

     b = models.ForeignKey(to="Business", to_field='id',on_delete=models.CASCADE)#报错加上了on_delete=models.CASCADE1
     #设置外键关联Business中的id字段也可写成b = models.ForeignKey('Business',to_field='id')

urls.py中（路由都在这里）：

 """untitled3 URL Configuration

 The `urlpatterns` list routes URLs to views. For more information please see:
     https://docs.djangoproject.com/en/2.0/topics/http/urls/
 Examples:
 Function views
     1. Add an import:  from my_app import views
     2. Add a URL to urlpatterns:  path('', views.home, name='home')
 Class-based views
     1. Add an import:  from other_app.views import Home
     2. Add a URL to urlpatterns:  path('', Home.as_view(), name='home')
 Including another URLconf
     1. Import the include() function: from django.urls import include, path
     2. Add a URL to urlpatterns:  path('blog/', include('blog.urls'))
 """
 from django.contrib import admin
 from django.urls import path
 from app01 import views
 from django.conf.urls import url

 urlpatterns = [
     path('admin/', admin.site.urls),
     url(r'^business/$',views.business),#$是结束符
 ]

views.py中(主要业务逻辑都在这里)：

 from django.shortcuts import render
 from app01 import models
 # Create your views here.
 def business(request):

     v1 = models.Business.objects.all()

     #QuerySet
     #[obj(id,caption,code),obj(id,caption,code),obj(id,caption,code)]  里面的小元素是对象

     v2 = models.Business.objects.values('id', 'caption')  # 拿固定列
     # QuerySet
     # [{'id':1,'caption':'xx','code':'da'},{....},{.....}]  里面的小元素是字典

     v3 = models.Business.objects.values_list('id', 'code')
     # QuerySet
     # [(1,开发),(2,运维)]  里面的小元素是字典

     return render(request,'business.html',{'v1':v1,'v2':v2,'v3':v3})   #注意：一定要加return   第一个参数request是对象不是字符串！不是字符串！不是字符串！

templates下的XXXX.html中（网页模板都放templates下）：

 <!DOCTYPE html>
 <html lang="en">
 <head>
     <meta charset="UTF-8">
     <title>Title</title>
 </head>
 <body>

 <h1> 对象 </h1>
 <ul>
     {% for row in v1 %}

      <li>   {{ row.caption }}-{{ row.code }}    </li>

     {% endfor %}
 </ul>

 <h1> 字典 </h1>

 <ul>
     {% for row in v2 %}

      <li>   {{ row.id }}-{{ row.caption }}    </li>

     {% endfor %}
 </ul>

 <h1> 元组 </h1>

 <ul>
     {% for row in v3 %}

      <li>   {{ row.0}}-{{ row.1 }}    </li>

     {% endfor %}
 </ul>

 </body>
 </html>