django_表的联合查询

一、django_自带的admin内存关联

                                          效果图

image.png

(1)、创建超级django自带的admin超级用户
python manage.py createsuperuser
(2).在app，admin中创建关联用户

from django.contrib import admin
from DbLoign import models
# Register your models here
admin.site.register(models.UserInfo)

(3)在models 创建表
关键词choicesuser_type_id = models.IntegerField(choices=user_type_choices,default=1)
创建一个对应元组

class UserInfo(models.Model):
    # 创建表需要用户名列，密码列，指定长度
    #create UserInfo(id int auto_increment pirmary key,username char(32),password char(64))、
    #Django 会默认创建自增列id
    username = models.CharField(max_length=32)
    password = models.CharField(max_length=60)
    email = models.CharField(max_length=50,null=True)
    user_type_choices =(
        (1,'超级用户'),
        (2,'普通用户'),
        (3,'puput'),
    )
    user_type_id = models.IntegerField(choices=user_type_choices,default=1)

二、非内存关联法

                                如图

image.png

(1)models.py 配置关键字 ForeignKey('类名'，to_field='字段')

Django 在帮生成关联字段的时候会在后面自动追加_id,
也就是下面代码中原本应生成user_city的字段，会自动追加成user_city_id

from django.db import models

# Create your models here.

class  city(models.Model):
    uid = models.IntegerField(primary_key=True)
    city_name = models.CharField(max_length=20)

class useInfos(models.Model):
    username = models.CharField(max_length=20)
    password = models.CharField(max_length=26)
    #和第一个表中的uid字段相互关联
    user_city = models.ForeignKey('city',to_field='uid')

其中city表如下：

image.png

userInfos表如下：

image.png

(2)views层如下：
主要知识点：

#想调用user_city字段给写成user_city_id
obj = models.useInfos.objects.filter(user_city_id=?)
#其中单指user_city包含了关联表中的字段，也就是city表中uid 和city_name
user_city = models.city.object.filter(uid=1).first
#models.city.object.filter(uid=1).first 中包含了city表中uid 和city_name

from django.shortcuts import render,redirect

# Create your views here.
from cmdb import models
def per_info(request):
    if request.method == 'GET':
        obj = models.useInfos.objects.all()
        #查询所有城市返回下拉框
        obj_city = models.city.objects.all()
        return  render(request,'info.html',{'msg':obj,'city':obj_city})
    elif request.method == 'POST':
        u = request.POST.get('username')
        p = request.POST.get('pwd')
        c = request.POST.get('city')
        models.useInfos.objects.create(
            username=u,
            password=p,
            user_city_id=c,
        )
        return redirect('/a/per_info')

(3)html如下：

    
    



    username
    

    pwd
    

    
        {% for i in city %}
        {{ i.city_name }}
        {% endfor %}
    
    

{% for i in msg %}
    {{i.username}}-{{ i.user_city.city_name }}
    

{% endfor %}