Django中數(shù)據(jù)庫的數(shù)據(jù)關(guān)系:一對(duì)一,一對(duì)多,多對(duì)多

更新時(shí)間：2018年10月21日 11:59:20 作者：回憶不說話

今天小編就為大家分享一篇關(guān)于Django中數(shù)據(jù)庫的數(shù)據(jù)關(guān)系:一對(duì)一,一對(duì)多,多對(duì)多，小編覺得內(nèi)容挺不錯(cuò)的，現(xiàn)在分享給大家，具有很好的參考價(jià)值，需要的朋友一起跟隨小編來看看吧

一對(duì)一：

一對(duì)一的關(guān)系極為一個(gè)數(shù)據(jù)僅對(duì)應(yīng)一個(gè)數(shù)據(jù)，用下圖的結(jié)構(gòu)圖可以幫助理解：

下面用代碼實(shí)現(xiàn)一下，首先要?jiǎng)?chuàng)建工程項(xiàng)目如下：

接著，我們定義模型：

來到models.py文件，創(chuàng)建兩個(gè)模型：

from django.db import models
# Create your models here.
class One(models.Model):
  oname = models.CharField(max_length=20,null=True)
  oage = models.CharField(max_length=20,null=True)
  odate = models.DateField(null=True)
class Two(models.Model):
# 設(shè)置一對(duì)一關(guān)系，是通過將表中的字段設(shè)置為主鍵完成的
# on_delete=models.CASCADE 當(dāng)父表中的某一條數(shù)據(jù)刪除的時(shí)候
  # 相關(guān)字表中的數(shù)據(jù)也會(huì)被刪除
  tsub = models.OneToOneField(One,on_delete=models.CASCADE,primary_key=True)
  tfond = models.CharField(max_length=20,null=True)
  tdes = models.CharField(max_length=200,null=True)

來到myPro文件夾下添加以下兩句代碼：

import pymysql
pymysql.install_as_MySQLdb()

下面可以遷移文件：

python manage.py makemigrations
python manage.py migrate

這樣我們就創(chuàng)建了兩個(gè)表：

來到views.py文件中添加數(shù)據(jù)，代碼如下：

from django.shortcuts import render
from .models import One,Two
# Create your views here.
def index(request):
  o1 = One.objects.create(oname='張三',oage=11,odate='2011-11-11')
  o2 = One.objects.create(oname='張三2',oage=12,odate='2012-12-12')
  t1 = Two.objects.create(tsub=o1,tfond='o1',tdes='我喜歡o1')
  t2 = Two.objects.create(tsub=o2,tfond='o2',tdes='我喜歡o2')
  return render(request,'index.html')

運(yùn)行之后，將添加數(shù)據(jù)的代碼注釋掉，否則后面每運(yùn)行一次都會(huì)添加。

下面，我們通過查詢數(shù)據(jù)來甄別其中的關(guān)系。

def select(request):
  t1 = Two.objects.get(tsub__oname = '張三')
  return render(request,'index.html',{'t1':t1})

一對(duì)多

即一個(gè)對(duì)象對(duì)應(yīng)著對(duì)個(gè)對(duì)象。

創(chuàng)建模型代碼：

from django.db import models
# Create your models here.
class People(models.Model):
  name = models.CharField(max_length=50)
  card_num = models.IntegerField(default=0)
class Card(models.Model):
  number = models.CharField(max_length=20)
  person = models.ForeignKey(People,on_delete=models.CASCADE)
  source = models.CharField(max_length=50)

urls.py路由設(shè)置：

from django.contrib import admin
from django.urls import path
from myApp import views
urlpatterns = [
  path('admin/', admin.site.urls),
  path('add/',views.add),
  path('select/',views.select),
]

views.py文件中代碼：

from django.shortcuts import render
from .models import People,Card
from django.http import HttpResponse
# Create your views here.
# 添加數(shù)據(jù)
def add(request):
  # p1 = People.objects.create(name='小王',card_num = 4)
  # p2 = People.objects.create(name='老王', card_num=40)
  #
  # c1 = Card(number='101',source = '中國銀行',person = p1)
  # c2 = Card(number='102', source='中國農(nóng)行', person=p1)
  # c3 = Card(number='110', source='中國建行', person=p1)
  # c1.save()
  # c2.save()
  # c3.save()
  #
  # c4 = Card(number='201', source='河南鄭州美容美發(fā)', person=p2)
  # c5 = Card(number='202', source='鄭州交通一卡通', person=p2)
  # c6 = Card(number='203', source='鄭州逍遙鎮(zhèn)胡辣湯', person=p2)
  # c7 = Card(number='204', source='鄭州惠濟(jì)四附院', person=p2)
  #
  # c4.save()
  # c5.save()
  # c6.save()
  # c7.save()
  return HttpResponse('添加成功')
def select(request):
  # 查找number=203的人
  c1 = Card.objects.get(number='203')
  print(c1.person.name)
  # 查找id為3對(duì)應(yīng)的人
  c2 = Card.objects.get(id=3)
  print(c2.person.name)
  # 查找c2的所有卡
  result = c2.person.card_set.all()
  print(result)
  for res in result:
    print(res.source)
  # 查找名字為老王的所有卡種
  result = People.objects.get(name='老王')
  for card in result.card_set.all():
    print(card.source)
  return HttpResponse('查詢成功')

多對(duì)多

即多個(gè)對(duì)象對(duì)應(yīng)對(duì)個(gè)對(duì)象，類似公交車坐車，人可以坐多個(gè)公交車，公交車也可以載不同的人。

創(chuàng)建模型代碼如下：

from django.db import models
# Create your models here.
class Publication(models.Model):
  pname = models.CharField(max_length=200)
  paddress = models.CharField(max_length=200)
class Book(models.Model):
  bname = models.CharField(max_length=200)
  bauthor = models.CharField(max_length=200)
  publication = models.ManyToManyField(Publication)

視圖文件views.py文件代碼如下：

from django.shortcuts import render
from .models import Publication,Book
from django.http import HttpResponse
# Create your views here.
def add(request):
  # p1 = Publication(pname='大象出版社',paddress='河南',)
  # p2 = Publication(pname='北京出版社',paddress='北京')
  # p3 = Publication(pname='清華出版社',paddress='河北')
  # p1.save()
  # p2.save()
  # p3.save()
  #
  # b1 = Book(bname='海底兩萬里',bauthor='趙四')
  # b2 = Book(bname='遮天',bauthor='辰東')
  # b3 = Book(bname='童年', bauthor='xxxx')
  # b4 = Book(bname='在人間', bauthor='yyyy')
  # b5 = Book(bname='我的大學(xué)', bauthor='張飛')
  # b6 = Book(bname='湯姆索亞歷險(xiǎn)記', bauthor='趙六兒')
  # b1.save()
  # b2.save()
  # b3.save()
  # b4.save()
  # b5.save()
  # b6.save()
  #
  # b1.publication.add(p1,p2,p3)
  # b2.publication.add(p1,p2)
  # b3.publication.add(p1,p3)
  # b4.publication.add(p2,p3)
  # b5.publication.add(p3)
  # 多對(duì)多關(guān)系，兩個(gè)表不直接產(chǎn)生聯(lián)系，而是將兩個(gè)表之間的關(guān)系記錄在中間表上
  # 中間表不需要?jiǎng)?chuàng)建，會(huì)自動(dòng)生成
  return HttpResponse('添加成功')
def select(request):
  # 通過書籍查找對(duì)應(yīng)的出版社
  b1 = Book.objects.get(bname='童年')
  # 獲取出版童年的所有出版社
  b1_publication = b1.publication.all()
  for pub in b1_publication:
    print(pub.pname)
    print(pub.paddress)
  p1 = Publication.objects.get(pname = '清華出版社')
  all_book = p1.book_set.all()
  print('------------------')
  for book in all_book:
    print(book.bname)
    print(book.bauthor)
  return HttpResponse('查找成功')

這樣，就介紹完了。

總結(jié)

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