淄博专业网站建设哪家专业/在线推广企业网站的方法

淄博专业网站建设哪家专业,在线推广企业网站的方法,企业品牌推广策划,网站开发的语言模型关系 1:1 一对一 （一个身份证对应一个驾照） 是使用外键唯一约束实现的对应最多只能有一个我们通常会在从表中声明关系主表，从表主表数据删除，从表数据级联删除从表数据删除，主表不受影响谁声明关系&#xff0c…

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模型关系

1:1 一对一（一个身份证对应一个驾照）

是使用外键+唯一约束实现的
对应最多只能有一个
我们通常会在从表中声明关系
- 主表，从表
主表数据删除，从表数据级联删除
从表数据删除，主表不受影响
谁声明关系，谁就是从表

 driver_idcard = models.OneToOneField(IDCard,on_delete=models.PROTECT)

主表获取从表数据，是通过隐性属性，隐性属性的名字默认是从表名字小写

  print(idcard.drivercard.driver_lever)

从表获取主表数据，是通过显性属性

print(dc.driver_idcard.id_name)

1:M（一个人对应多辆车）

使用外键实现的
主表获取从表是隐性属性，隐性属性是Manager的子类
- 支持
  - all
  - filter
  - first
  - last
数据删除和一对一一样

  - 从表获取主表数据，是通过显性属性idcard = car.c_idcardprint(idcard.id_name- 主表获取从表数据，是通过隐性属性，隐性属性的名字 默认是从表名字小写idcard = IDCard.objects.last()cars = idcard.car_set.last()

实例

models.py

from django.db import models# Create your models here.
class IDCard(models.Model):id_num = models.CharField(max_length=32,unique=True)id_name = models.CharField(max_length=32)class DriverCard(models.Model):diver_leverl = models.CharField(max_length=16)driver_idcard = models.OneToOneField(IDCard,on_delete=models.PROTECT)class Car(models.Model):c_type = models.CharField(max_length=32)c_idcard = models.ForeignKey(IDCard,null=True)

view.py

import random
import uuidfrom django.http import HttpResponse
from django.shortcuts import render# Create your views here.
from RelationLearn.models import IDCard, DriverCard, Cardef index(request):return HttpResponse("three index")def add_idcard(request):id_card = IDCard()id_card.id_num = random.randrange(10000000000)id_card.id_name = uuid.uuid4().hexid_card.save()return HttpResponse("add new id card ok")def add_dc(request):dc = DriverCard()dc.diver_level = "c1"id_card = IDCard.objects.last()dc.driver_idcard =id_carddc.save()return HttpResponse("add killer  ok")def delete_idcard(request):id_card = IDCard.objects.last()id_card.delete()return HttpResponse("del idcard  ok")def del_dc(request):dc_card = DriverCard.objects.last()dc_card.delete()return HttpResponse("del dc  ok")def get_idcard(request):dc= DriverCard.objects.last()print(dc.driver_idcard.id_name)return HttpResponse("by carid get id")def get_dc(request):idcard= IDCard.objects.last()print(idcard.drivercard.driver_lever)return HttpResponse("by id get carid")def get_idcard_form_car(request):car =Car.objects.last()idcard = car.c_idcardprint(idcard.id_name)return HttpResponse("by car gei id ")def get_car(request):idcard = IDCard.objects.last()cars = idcard.car_set.last()for car in cars:print(car)car_single = idcard.car_set.first()print(car_single.c_type)return HttpResponse("get cars by id")def add_car(request):# car = Car()# car.c_type = "tiganche"# idcard = IDCard.objects.last()# car.c_idcard = idcard# car.save()car = Car()car.c_type = "olddriver"car.save()idcard = IDCard.objects.last()idcard.car_set.add(car)return HttpResponse("add car ")

M:N
- 使用额外的关系表进行数据记录
- 关系表使用两个外键实现的

from django.db import models# Create your models here.
class BlogUser(models.Model):u_name =models.CharField(max_length=32)class Blog(models.Model):b_title =models.CharField(max_length=64)b_content =models.TextField()b_user_collect =models.ManyToManyField(BlogUser)

views.py

from django.http import HttpResponse
from django.shortcuts import render# Create your views here.
from ManyLearn.models import *def index(request):return HttpResponse("index many")def add_collect(request):# blog = Blog.objects.last()# # blog= Blog()# user =BlogUser.objects.first()# blog.b_user_collect.add(user)# return HttpResponse("add collect")blog = Blog.objects.last()user = BlogUser.objects.last()user.blog_set.add(blog)return HttpResponse("add collect")def del_collects(request):blog = Blog.objects.all()user = BlogUser.objects.get(id = "3")user.blog_set.remove(*blog)return HttpResponse("del collects ok")
# 查询指定用户的收藏的所有博客
def get_usercollects(request):user = BlogUser.objects.first()# print(user.blog_set.all().values())collections = user.blog_set.all()return render(request,"AllCollects.html",context=locals())
# 查询指定博客被哪些用户收藏了
def get_user(request):blog = Blog.objects.first()# blog=Blog()users = blog.b_user_collect.all()return render(request,"AllCollectsUser.html",context=locals())