数据库引擎的设置
打开mysite/settings.py配置文件，默认配置的数据库是SQLite.如果需要修改使用别的数据库，那么修改配置文件里的DATABASES ‘default‘，里面有如下几个选项:
ENGINE-可以选择‘django.db.backends.sqlite3‘, ‘django.db.backends.postgresql‘, ‘django.db.backends.mysql‘, or ‘django.db.backends.oracle‘或者别的数据库
NAME-数据库的名称。如果你使用SQLite，数据库将会是你电脑上的某个文件。换句话说，NAME应该是一个完整的文件的名称及绝对路径的组合。默认的值os.path.join(BASE_DIR, ‘db.sqlite3‘)是会生成在你的项目目录下的
假如你使用的是别的数据库，那么别的选项例如 USER, PASSWORD, 以及 HOST一定要有。
可以在配置文件mysite/settings.py里通过TIME_ZONE配置项来配置自己应用的时区
注意一下配置文件的INSTALLED_APPS配置项，里面是如今所有已经集成在应用里的模块。
默认情况下，INSTALLED_APPS包括下面的模块:
django.contrib.admin -django内置的管理后台
django.contrib.auth-django的认证系统
django.contrib.contenttypes-各种内容框架
django.contrib.sessions -django的sessions模块
django.contrib.messages-django的消息框架
django.contrib.staticfiles -django的管理静态文件的模块
数据库表的创建
python manage.py migrate
建立数据库模型
在poll项目中我们创建2个模型:Question及Choice。一个Question包括一个问题及发布的时间。一个Choice有2个属性:选项及总票数。每个Choice是和Question绑定在一起的
上述这些文字描述都可以在Python类中表达出来，如下polls/models.py:
from django.db import models
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField(‘date published‘)
class Choice(models.Model):
question = models.ForeignKey(Question, on_delete=models.CASCADE)
choice_text = models.CharField(max_length=200)
votes = models.IntegerField(default=0)
每个模型都是继承自类django.db.models.Model.每个模型又包括了很多属性值也就是数据库中的字段每个field都代表了一个Field类的一个实例，比如CharField代表character,DateTimeField代表日期。这些用来区分字段的类型一些field可以设置一些属性值，比如CharField可以设置max_length，我们设置votes这个属性的defalut值为0最后我们注意定义一个2者之间的联系，使用ForeignKey,这个告诉django，每个Choice被绑定到一个Question上。django支持多种一般数据库的关系:多对一，多对多，一对多激活
模型激活
首先我们应该告诉django，我们polls这个应用被引入到diango中
在mysite/settings.py文件中加入如下一行‘polls.apps.PollsConfig‘,然后代码会显示成如下:
INSTALLED_APPS = [ ‘polls.apps.PollsConfig‘, ‘django.contrib.admin‘, ‘django.contrib.auth‘, ‘django.contrib.contenttypes‘, ‘django.contrib.sessions‘, ‘django.contrib.messages‘, ‘django.contrib.staticfiles‘, ]
然后运行如下命令，告知django，我们的数据库有了新的变动:
python manage.py makemigrations polls
生成数据库表，运行如下命令:
python manage.py migrate
通过如上学习，可以知道在数据库中生成表结构可以按照如下步骤:
在models.py中新建自己的数据模型
运行python manage.py makemigrations 来告知django数据模型变动
运行 python manage.py migrate去在数据库生成表结构
通过django自带的数据库API来调试
通过如下命令进入调试模式:
python manage.py shell
按照如下进行尝试:
>>> from polls.models import Choice, Question # Import the model classes we just wrote. # No questions are in the system yet. >>> Question.objects.all() <QuerySet []> # Create a new Question. # Support for time zones is enabled in the default settings file, so # Django expects a datetime with tzinfo for pub_date. Use timezone.now() # instead of datetime.datetime.now() and it will do the right thing. >>> from django.utils import timezone >>> q = Question(question_text="What‘s new?", pub_date=timezone.now()) # Save the object into the database. You have to call save() explicitly. >>> q.save() # Now it has an ID. >>> q.id 1 # Access model field values via Python attributes. >>> q.question_text "What‘s new?" >>> q.pub_date datetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=<UTC>) # Change values by changing the attributes, then calling save(). >>> q.question_text = "What‘s up?" >>> q.save() # objects.all() displays all the questions in the database. >>> Question.objects.all() <QuerySet [<Question: Question object (1)>]>
稍等一下,<Question: Question object (1)>的显示对我们来讲并不友好，我们修改一下Question模型及Choice的代码，修改polls/models.py，新增如下:
from django.db import models class Question(models.Model): # ... def __str__(self): return self.question_text class Choice(models.Model): # ... def __str__(self): return self.choice_text
我们给model新建一个自定义的方法,polls/models.py:
import datetime from django.db import models from django.utils import timezone class Question(models.Model): # ... def was_published_recently(self): return self.pub_date >= timezone.now() - datetime.timedelta(days=1)
然后我们重新运行python manage.py shell :
>>> from polls.models import Choice, Question # Make sure our __str__() addition worked. >>> Question.objects.all() <QuerySet [<Question: What‘s up?>]> # Django provides a rich database lookup API that‘s entirely driven by # keyword arguments. >>> Question.objects.filter(id=1) <QuerySet [<Question: What‘s up?>]> >>> Question.objects.filter(question_text__startswith=‘What‘) <QuerySet [<Question: What‘s up?>]> # Get the question that was published this year. >>> from django.utils import timezone >>> current_year = timezone.now().year >>> Question.objects.get(pub_date__year=current_year) <Question: What‘s up?> # Request an ID that doesn‘t exist, this will raise an exception. >>> Question.objects.get(id=2) Traceback (most recent call last): ... DoesNotExist: Question matching query does not exist. # Lookup by a primary key is the most common case, so Django provides a # shortcut for primary-key exact lookups. # The following is identical to Question.objects.get(id=1). >>> Question.objects.get(pk=1) <Question: What‘s up?> # Make sure our custom method worked. >>> q = Question.objects.get(pk=1) >>> q.was_published_recently() True # Give the Question a couple of Choices. The create call constructs a new # Choice object, does the INSERT statement, adds the choice to the set # of available choices and returns the new Choice object. Django creates # a set to hold the "other side" of a ForeignKey relation # (e.g. a question‘s choice) which can be accessed via the API. >>> q = Question.objects.get(pk=1) # Display any choices from the related object set -- none so far. >>> q.choice_set.all() <QuerySet []> # Create three choices. >>> q.choice_set.create(choice_text=‘Not much‘, votes=0) <Choice: Not much> >>> q.choice_set.create(choice_text=‘The sky‘, votes=0) <Choice: The sky> >>> c = q.choice_set.create(choice_text=‘Just hacking again‘, votes=0) # Choice objects have API access to their related Question objects. >>> c.question <Question: What‘s up?> # And vice versa: Question objects get access to Choice objects. >>> q.choice_set.all() <QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]> >>> q.choice_set.count() 3 # The API automatically follows relationships as far as you need. # Use double underscores to separate relationships. # This works as many levels deep as you want; there‘s no limit. # Find all Choices for any question whose pub_date is in this year # (reusing the ‘current_year‘ variable we created above). >>> Choice.objects.filter(question__pub_date__year=current_year) <QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]> # Let‘s delete one of the choices. Use delete() for that. >>> c = q.choice_set.filter(choice_text__startswith=‘Just hacking‘) >>> c.delete()
使用Django Admin
创建一个管理用户
在项目下运行如下命令:
python manage.py createsuperuser
然后输入用户名，email及密码，然后使用如下命令启动项目:
python manage.py runserver
我们等待启动后，在浏览器中访问http://127.0.0.1:8000/admin/，输入刚才的用户及密码登录
然后把我们自己新建的模型注册到django的管理后台中,使用如下命令,在polls/admin.py:
from django.contrib import admin from .models import Question admin.site.register(Question)
然后我们可以自由操作后管，自行做一些练习
原文：https://www.cnblogs.com/doumayi/p/12871274.html