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>