Django基于ORM操作数据库的方法详解

vim settings #HelloWorld/HelloWorld目录下

DATABASES = {
  'default': {
    'ENGINE': 'django.db.backends.mysql',#mysql数据库中第一个库test
    'NAME': 'test','USER': 'root','PASSWORD': '123456','HOST':'127.0.0.1','PORT':'3306',},'article': {
    'ENGINE': 'django.db.backends.mysql',# mysql数据库中第二个库test2
    'NAME': 'test2',}
}

django-admin.py startapp blog ##HelloWorld/目录下建立网站app，我建了两个app（blog和article）

vim settings ##/HelloWorld/HelloWorld目录下

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

vim models.py ##blog目录下

from django.db import models
# Create your models here.
class Teacher(models.Model):
  id = models.IntegerField(primary_key=True)
  name = models.CharField(max_length=50)
  class Meta:
    db_table = 'teacher'#默认库test中建立名为teacher的表。字段就是id和name

python manage.py migrate ##建立Django系统表，首次运行即可
python manage.py makemigrations ##生成迁移计划，每次加表或字段时都运行生成计划
python manage.py migrate ##同步用户定义的表

vim models.py #blog目录下，新建个表测试下，可以在添加或修改删除几个字段试试

class Student(models.Model):
  id = models.IntegerField(primary_key=True)
  name = models.CharField(max_length=50)
  student_number = models.CharField(default="",max_length=50)
  class Meta:
    db_table = 'student'

cd article #进入article目录
vim models.py #article目录下

from django.db import models
class Author(models.Model):
  id = models.IntegerField(primary_key=True)
  name = models.CharField(max_length=50)
  author_ids = models.CharField(max_length=50)
  class Meta:
    db_table = 'author'
    app_label = 'article' ##对应的article这个应用，名字要一致

python manage.py makemigrations article ##生成同步计划
##对article应用执行同步，同步到 article（settings中的配置，对应test2）对应的数据库中.
python migrate article --database article ##执行计划，必须加--database 指定要同步的库

cd blog #进入blog目录下
vim models.py ##blog目录下，在文件中增加一个表，注意后边app_label

class Group(models.Model):
  id = models.IntegerField(primary_key=True)
  group_name = models.CharField(max_length=50)
  class Meta:
    db_table = 'group'
    app_label = 'article' ##必须指定这个库

python manage.py makemigrations article ##生成同步计划，虽说改的是blog
python migrate article --database article ##执行计划，虽说改的是blog

vim view.py ##blog目录下，添加下列代码

from blog.models import Teacher
def orm_handle_db(request):
  test1 = Teacher(id=1,name='runoob',teacher_number='10') ##定义数据
  test1.save() ##保存
  return render_to_response('orm_handle_db.html')

vim urls.py ##blog目录下

from django.conf.urls import url
from blog import views
urlpatterns = [
  url(r'^hello/$',views.hello),url(r'^search/$',views.search),url(r'^post_search/$',views.post_search),url(r'^search_submit$',views.search_submit),url(r'^post_search_submit$',views.post_search_submit),url(r'^db_handle/$',views.db_handle),url(r'^orm_handle_db/$',views.orm_handle_db),##这里配置好
]

vim orm_handle_db.html ##blog/templates目录下

vim settings.py ##HelloWorld/HelloWorld目录下，添加下面两项

DATABASES_APPS_MAPPING = {
  'blog': 'default','article': 'article',}
DATABASE_ROUTERS = ['HelloWorld.database_app_router.DatabaseAppsRouter']

vim database_app_router.py ##配置路由,HelloWorld/HelloWorld/目录下。直接粘贴

from django.conf import settings
class DatabaseAppsRouter(object):
def db_for_read(self,model,**hints):
app_label = model._meta.app_label
if app_label in settings.DATABASES_APPS_MAPPING:
res = settings.DATABASES_APPS_MAPPING[app_label]
print(res)
return res
return None
def db_for_write(self,**hints):
app_label = model._meta.app_label
if app_label in settings.DATABASES_APPS_MAPPING:
return settings.DATABASES_APPS_MAPPING[app_label]
return None
def allow_relation(self,obj1,obj2,**hints):
db_obj1 = settings.DATABASES_APPS_MAPPING.get(obj1._mata.app_label)
db_obj2 = settings.DATABASES_APPS_MAPPING.get(obj2._mata.app_label)
if db_obj1 and db_obj2:
if db_obj1 == db_obj2:
return True
else:
return False
return None
def db_for_migrate(self,db,app_label,model_name=None,**hints):
if db in settings.DATABASES_APPS_MAPPING.values():
return settings.DATABASES_APPS_MAPPING.get(app_label) == db
elif app_label in settings.DATABASES_APPS_MAPPING:
return False
return None

vim views.py #blog目录下，添加下方代码

from blog.models import Teacher,Group##这是第8步没有的
def orm_handle_db(request):
  test1 = Teacher(id=1,teacher_number='10')
  test2 = Group(id=1,group_name='runoob') ##这是第8步没有的
  test1.save()
  test2.save()##这是第8步没有的
  return render_to_response('orm_handle_db.html')