模型關系

1:1 一對一 （一個身份證對應一個駕照）

• 是使用外鍵+唯一約束實現(xiàn)的
• 對應最多只能有一個
• 我們通常會在從表中聲明關系
  • 主表，從表
• 主表數據刪除，從表數據級聯(lián)刪除
• 從表數據刪除，主表不受影響
• 誰聲明關系，誰就是從表

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

• 主表獲取從表數據，是通過隱性屬性，隱性屬性的名字 默認是從表名字小寫

print(idcard.drivercard.driver_lever)

• 從表獲取主表數據，是通過顯性屬性

print(dc.driver_idcard.id_name)

1:M（一個人對應多輛車）

• 使用外鍵實現(xiàn)的
• 主表獲取從表是隱性屬性，隱性屬性是Manager的子類
  • 支持
    • all
    • filter
    • first
    • last
• 數據刪除和一對一一樣

- 從表獲取主表數據，是通過顯性屬性idcard = car.c_idcardprint(idcard.id_name- 主表獲取從表數據，是通過隱性屬性，隱性屬性的名字 默認是從表名字小寫idcard = IDCard.objects.last()cars = idcard.car_set.last()

實例

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
  • 使用額外的關系表進行數據記錄
  • 關系表使用兩個外鍵實現(xiàn)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") # 查詢指定用戶的收藏的所有博客 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()) # 查詢指定博客被哪些用戶收藏了 def get_user(request):blog = Blog.objects.first()# blog=Blog()users = blog.b_user_collect.all()return render(request,"AllCollectsUser.html",context=locals())

模型級聯(lián)操作

• CASECADE
  • 默認模式
  • 默認級聯(lián)刪除
• PROTECT
  • 保護模式
  • 存在級聯(lián)數據就不能刪除
  • 不存在級聯(lián)數據就可以刪除
• SET
  • 設置為某值
  • NULL
    • 字段允許為空
  • DEFAULT
    • 字段存在默認值
  • VALUE
    • VALUE是真實的值

總結

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