Python 【第十四章】django 数据操作之model 之多对多操作

model多对多操作
- 创建
a. 方式一：
class B2G(models.Model):                  #人工创建第三张表
b_id = models.ForeignKey('Boy')
g_id = models.ForeignKey('Girl')

class Boy(models.Model):

username = models.CharField(max_length=16)

class Girl(models.Model):

name = models.CharField(max_length=16)

b. 方式二：
class Boy(models.Model):

username = models.CharField(max_length=16)
# girl_set
class Girl(models.Model):

name = models.CharField(max_length=16)

b = models.ManyToManyField('Boy')     #由django自动创建 第三张表

 多对多例：

models.py

class Boy(models.Model):

    username = models.CharField(max_length=16)
    # girl_set
class Girl(models.Model):
    name = models.CharField(max_length=16)
    b = models.ManyToManyField('Boy')

urls.py

from django.conf.urls import url
from django.contrib import admin
from app01 import views

urlpatterns = [
    # url(r'^admin/', admin.site.urls),
    url(r'^index/',views.index),
    url(r'^add_user_type/',views.add_user_type),
    url(r'^add_boy/', views.add_boy),
    url(r'^add_girl/', views.add_girl),
    url(r'^boy_to_girl/', views.boy_to_girl),
]

views.py

from django.shortcuts import render
from django.shortcuts import HttpResponse
from app01 import models
from django import forms


def add_user_type(request):
    q = request.GET.get('q', None)
    if q:
        models.UserType.objects.create(caption=q)
    return HttpResponse(q)

def add_boy(request):
    boy = request.GET.get('v',None)
    if boy:
        models.Boy.objects.create(username=boy)
    return HttpResponse(boy)

def add_girl(request):
    girl = request.GET.get('v',None)
    if girl:
        models.Girl.objects.create(name=girl)
    return HttpResponse(girl)

def boy_to_girl(request):
    g1 = models.Girl.objects.get(id=1)
    print("女",g1.name)
    return HttpResponse("ok")

不用创建html文件，

直接浏览器输入add_boy/?v=李四和add_girl/?v=小红  可以对数据库添加 数据

 然后 http://127.0.0.1:8000/boy_to_girl/ 可以取得数据

 

 views.py中取出

def boy_to_girl(request):
    g1 = models.Girl.objects.get(id=1)
    print("女",g1.name)
    return HttpResponse("ok")

输出 效果

 

veiws.py中实现关联第三张表

def boy_to_girl(request):
    g1 = models.Girl.objects.get(id=1)
    print('女孩',g1.name)
    #g1.b是多对多字段
    #g1.b.add('男')
    b1 = models.Boy.objects.get(id=1)
    g1.b.add(b1)
    return  HttpResponse("OK")

获取关联数据

veiws.py

def boy_to_girl(request):
    # g1 = models.Girl.objects.get(id=1)
    # print('女孩',g1.name)
    # #g1.b是多对多字段
    # #g1.b.add('男')
    # b1 = models.Boy.objects.get(id=1)
    # g1.b.add(b1)
    g1 = models.Girl.objects.get(id=1)
    ret = g1.b.all() #获取第三张表中girl_id = 1 所有数据
    print(ret)  
    return  HttpResponse("OK")

 再添加 关联，一个女对id 2的男

views.py

def boy_to_girl(request):
    g1 = models.Girl.objects.get(id=1)
    print('女孩',g1.name)
    #g1.b是多对多字段
    #g1.b.add('男')
    b1 = models.Boy.objects.get(id=2)
    g1.b.add(b1)
    g1 = models.Girl.objects.get(id=1)
    ret = g1.b.all() #获取第三张表中girl_id = 1 所有数据
    print(ret)
    return  HttpResponse("OK")

输出 结果 

操作：

添加：
正向

########### 增加数据 ###########
# 获取一个女孩对象
g1 = models.Girl.objects.get(id=1)

# 获取一个男孩对象
b1 = models.Boy.objects.get(id=1)

# 利用对对多字段b将男孩和女孩建立关系
g1.b.add(models.Boy.objects.get(id=1))
g1.b.add(1)

#一个女孩对所有男孩
bs = models.Boy.objects.all()
g1.b.add(*bs)
g1.b.add(*[1,2,3])

反向
b1 = models.Boy.objects.get(id=1)
b1.girl_set.add(1)       #girl_set 是boy表中隐含
b1.girl_set.add(models.Girl.objects.all())

b1.girl_set.add(*[1,2,3,4])

删除：
g1 = models.Girl.objects.get(id=1)
g1.b.clear() # 清空和girl ID=1所关联的所有数据

例如：

def boy_to_girl(request):
    # g1 = models.Girl.objects.get(id=1)
    # print('女孩',g1.name)
    # #g1.b是多对多字段
    # #g1.b.add('男')
    # b1 = models.Boy.objects.get(id=2)
    # g1.b.add(b1)
    # g1 = models.Girl.objects.get(id=1)
    # ret = g1.b.all() #获取第三张表中girl_id = 1 所有数据
    # print(ret)
    
    # 删除第三张表中和女孩1关联的所有关联信息
    g1 = models.Girl.objects.get(id=1)
    g1.b.clear()
    # 查询和女孩1关联所有男孩
    g1 = models.Girl.objects.get(id=1)
    boy_list = g1.b.all()
    # for item in boy_list:
    #     print(item)
    print(boy_list)

    return  HttpResponse("OK")

g1.b.remove(2)
g1.b.remove(*[1,2])

备注： 同样也支持反向操作

查询：

正向查
g1 = models.Girl.objects.get(id=1) # SQL
g1.b.all() # SQL
g1.b.filter().count()

例子：

def add_girl(request):
    girl = request.GET.get('v',None)
    if girl:
        models.Girl.objects.create(name=girl)
    return HttpResponse(girl)

def boy_to_girl(request):
    # g1 = models.Girl.objects.get(id=1)
    # print('女孩',g1.name)
    # #g1.b是多对多字段
    # #g1.b.add('男')
    # b1 = models.Boy.objects.get(id=2)
    # g1.b.add(b1)
    # g1 = models.Girl.objects.get(id=1)
    # ret = g1.b.all() #获取第三张表中girl_id = 1 所有数据
    # print(ret)

    # # 删除第三张表中和女孩1关联的所有关联信息
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.clear()
    # # # 查询和女孩1关联所有男孩
    # g1 = models.Girl.objects.get(id=1)
    # boy_list = g1.b.all()
    # g1.b.remove(1)
    # print(boy_list)
    #添加和女孩1和 男孩1，2，3关联
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.add(*[1,2,3])
    g1 = models.Girl.objects.get(id=1)
    ret = g1.b.filter().count()
    print(ret)
    return  HttpResponse("OK")

反向查
b1 = models.Boy.objects.get(id=1)
b1.girl_set.all()

产生第三张表自动关联查询

models.Girl.objects.all().values('id','name', 'b__username')

例子：

def boy_to_girl(request):
    # g1 = models.Girl.objects.get(id=1)
    # print('女孩',g1.name)
    # #g1.b是多对多字段
    # #g1.b.add('男')
    # b1 = models.Boy.objects.get(id=2)
    # g1.b.add(b1)
    # g1 = models.Girl.objects.get(id=1)
    # ret = g1.b.all() #获取第三张表中girl_id = 1 所有数据
    # print(ret)

    # # 删除第三张表中和女孩1关联的所有关联信息
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.clear()
    # # # 查询和女孩1关联所有男孩
    # g1 = models.Girl.objects.get(id=1)
    # boy_list = g1.b.all()
    # g1.b.remove(1)
    # print(boy_list)
    #添加和女孩1和 男孩1，2，3关联
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.add(*[1,2,3])
    # g1 = models.Girl.objects.get(id=1)
    # ret = g1.b.filter().count()
    ret = models.Girl.objects.all().values('id','name', 'b__username')
    print(ret)
    return  HttpResponse("OK")

 读取产生SQL语句

models.Boy.objects.all().values('id','username', 'girl__name')

def boy_to_girl(request):
    # g1 = models.Girl.objects.get(id=1)
    # print('女孩',g1.name)
    # #g1.b是多对多字段
    # #g1.b.add('男')
    # b1 = models.Boy.objects.get(id=2)
    # g1.b.add(b1)
    # g1 = models.Girl.objects.get(id=1)
    # ret = g1.b.all() #获取第三张表中girl_id = 1 所有数据
    # print(ret)

    # # 删除第三张表中和女孩1关联的所有关联信息
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.clear()
    # # # 查询和女孩1关联所有男孩
    # g1 = models.Girl.objects.get(id=1)
    # boy_list = g1.b.all()
    # g1.b.remove(1)
    # print(boy_list)
    #添加和女孩1和 男孩1，2，3关联
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.add(*[1,2,3])
    # g1 = models.Girl.objects.get(id=1)
    # ret = g1.b.filter().count()
    ret = models.Boy.objects.all().values('id','username', 'girl__name')
    print(ret)
    return  HttpResponse("OK")

 读取产生SQL语句

输入结果

System check identified no issues (0 silenced).
January 30, 2017 - 23:49:26
Django version 1.10.4, using settings 'untitled2.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK.
SELECT "app01_boy"."id", "app01_boy"."username", "app01_girl"."name" FROM "app01_boy" LEFT OUTER JOIN "app01_girl_b" ON ("app01_boy"."id" = "app01_girl_b"."boy_id") LEFT OUTER JOIN "app01_girl" ON ("app01_girl_b"."girl_id" = "app01_girl"."id")
[30/Jan/2017 23:49:38] "GET /boy_to_girl/ HTTP/1.1" 200 2

 ————————————————————————————————————————————————————

 添加例子

def boy_to_girl(request):
    
    #添加和女孩1和 男孩1，2，3关联
    g1 = models.Girl.objects.get(id=1)
    g1.b.add(*[1,2,3])

    return  HttpResponse("OK")

查询

def boy_to_girl(request):
    # g1 = models.Girl.objects.get(id=1)
    # print('女孩',g1.name)
    # #g1.b是多对多字段
    # #g1.b.add('男')
    # b1 = models.Boy.objects.get(id=2)
    # g1.b.add(b1)
    # g1 = models.Girl.objects.get(id=1)
    # ret = g1.b.all() #获取第三张表中girl_id = 1 所有数据
    # print(ret)

    # # 删除第三张表中和女孩1关联的所有关联信息
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.clear()
    # # # 查询和女孩1关联所有男孩
    g1 = models.Girl.objects.get(id=1)
    boy_list = g1.b.all()
    # # # for item in boy_list:
    # # #     print(item)
    print(boy_list)
    #添加和女孩1和 男孩1，2，3关联
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.add(*[1,2,3])

    return  HttpResponse("OK")

 

删除1 个

def boy_to_girl(request):
    # g1 = models.Girl.objects.get(id=1)
    # print('女孩',g1.name)
    # #g1.b是多对多字段
    # #g1.b.add('男')
    # b1 = models.Boy.objects.get(id=2)
    # g1.b.add(b1)
    # g1 = models.Girl.objects.get(id=1)
    # ret = g1.b.all() #获取第三张表中girl_id = 1 所有数据
    # print(ret)

    # # 删除第三张表中和女孩1关联的所有关联信息
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.clear()
    # # # 查询和女孩1关联所有男孩
    g1 = models.Girl.objects.get(id=1)
    boy_list = g1.b.all()
    g1.b.remove(1)
    print(boy_list)
    #添加和女孩1和 男孩1，2，3关联
    # g1 = models.Girl.objects.get(id=1)
    # g1.b.add(*[1,2,3])

    return  HttpResponse("OK")