计算机基础知识50

数据的增删改查(insert update delete select)

# 用户列表的展示：
# 把数据表中得用户数据都给查询出来展示在页面上

1. 查询
from app01 import models
models.UserInfo.objects.all() # 查询所有的字段信息和数据
res=models.UserInfo.objects.first() # 查询一条，而且是第一条，queryset对象，列表套对象的形式
if res:res[0]
try:res[0]
# 它是支持索引取值的，如果是第一条就直接first()
select * from userinfo where username ='' and password = '';
res=models.UserInfo.objects.filter(username='', password='').first()  # and
res=models.UserInfo.objects.filter(username='').filter(password='').filter().first() # and
"""链式表达式的思想，jQuery中也有这样的写法"""
models.UserInfo.objects.all()[0]
models.UserInfo.objects.all()[0:2] # 支持切片
2. 增加
models.UserInfo.objects.create(username='', password='')
res=models.UserInfo(username='', password='')
res.save() # 真正的操作数据库
3、修改数据的逻辑分析
# 1. 先确定修改哪条记录------>怎么样确定修改哪条记录?
# 2. 通过什么字段可以确定唯一一条记录? 主键id，要携带主键id到后端.
# 3. 在后端接收主键id值，然后根据这个id值再去表中查询数据，查询一条
# 4. 然后把查询的数据在渲染到页面中，然后在修改
models.UserInfo.objects.filter(pk=1).update(username='', password='')
res=models.UserInfo.objects.first()
res.username='';
res.password=''
res.save()    # 真正的操作数据库
4、删除功能的分析

# 1. 给删除按钮加一个链接，携带当前记录的id值
# 2. 后端要接收这个主键id值
# 3. 后端直接执行删除操作
models.UserInfo.objects.filter(pk=1).delete()
res.delete()

数据的增删改查汇总

"views.py"

from django.shortcuts import render,HttpResponse,reverse,redirect# Create your views here.def home(request):print('request')return HttpResponse('/home/')from app01 import modelsdef login(request):print(request.method,type(request.method))if request.method == 'POST':username = request.POST.get('username')password = request.POST.get('password')print(request.POST.getList('hobby'))res = models.UserInfo.objects.filter(username='123',password='123').all()print(res)res.username=''res.password=''if username == 'kevin' and password == '123':print('登录成功')models.UserInfo.objects.create(username='kevin',password='123')return redirect('/index/')else:return HttpResponse("用户名或密码错误")print(request.GET)print(request.GET.get('a'))print(request.GET.get('b'))print(request.GET.get('c'))print(request.GET.get('c'))print(request.GET.getlist('c'))return render(request,'login.html')def userlist(request):user_list=models.UserInfo.objects.all()#查询所有信息"""这里不之处负数切片"""# user_list=models.UserInfo.objects.all()[0:2] # 查询所有的数据'''支持for循环'''# for i in user_list:#     print(i.gender)## queryset对象就是一个列表套对象的形式# <QuerySet [<UserInfo: UserInfo object>, <UserInfo: UserInfo object>, <UserInfo: UserInfo object>]># print(user_list[0])print(user_list[0].username)return  render(request,'userlist.html',locals())def edit(request):edit_id = request.GET.get('id')edit_ibj = models.UserInfo.objects.filter(id=edit_id).first()if request.method == 'POST':hidden_id = request.POST.get('hidden_id')username = request.POST.get('username')password = request.POST.get('password')gender = request.POST.get('gender')# 修改affect_rows = models.UserInfo.objects.filter(pk=hidden_id).update(username=username,password=password,gender=gender)return redirect('/userlist/')return render(request,'edit.html',locals())def delete(request):delete_id = request('/userlist/')return redirect('/userlist/')def add(request):if request.method == 'POST':username = request.POST.get('username')password = request.POST.get('password')gender = request.POST.get('gender')user_obj = models.UserInfo(username=username,password=password,gender=gender)user_obj.save()return redirect('/userlist/')return render(request,'add.html')def ab_render(request):user_dict1 = {'username':'kevin','password':123}user_dict1 = {'a':1}print(locals())return render(request,'')

"urls.py"


from django.contrib import admin
from django.urls import path
from app01 import viewsurlpatterns = [path('admin/', admin.site.urls),path('login/', views.login),path('home/', views.home),path('userlist/', views.userlist),path('edit/', views.edit),path('delete/', views.delete),path('add/', views.add),path('ab_render/', views.ab_render),]

"models.py"

from django.db import models# Create your models here.class UserInfo(models.Model):username = models.CharField(max_length=32,verbose_name='用户名')password = models.CharField(max_length=64,verbose_name='密码')gender = models.CharField(max_length=32)def __str__(self):return self.username

"__init__.py"

import pymysql
pymysql.install_as_MySQLdb()

前端："ab_render.html"

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.7.1/jquery.min.js"></script><link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"><script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>{{ user_dict.username }}
{{ user_dict.password }}
{{ user_dict1 }}
{{ user_dict1.a }}
</body>
</html>

"add.html"

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.7.1/jquery.min.js"></script><link rel="stylesheet" href="bootstrap-3.4.1-dist/css/bootstrap.min.css"><script src="bootstrap-3.4.1-dist/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container"><div class="row"><h1 class="text-center">添加页面</h1><form action="" method="post"><div class="form-group">用户名：<input type="text" class="form-control" name="username"></div><div class="form-group">密码：<input type="password" class="form-control" name="password"></div><div class="form-group">性别：<input type="text" class="form-control" name="gender"></div></form></div>
</div>
</body>
</html>

"edit.html"

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.7.1/jquery.min.js"></script><link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"><script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container"><div class="row"><h1 class="text-center">修改页面</h1><form action="" method="post"><input type="hidden" value="{{ edit_obj.pk }}" name="hidden_id"><div class="form-group">用户名： <input type="text" class="form-control" name="username" value="{{ edit_obj.username }}"></div><div class="form-group">密码： <input type="password" class="form-control" name="password" value="{{ edit_obj.password }}"></div><div class="form-group">性别： <input type="text" class="form-control" name="gender" value="{{ edit_obj.gender }}"></div><div class="form-group"><input type="submit" class="btn btn-info btn-block" value="提交"></div></form></div>
</div>
</body>
</html>

"index.html"

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.7.1/jquery.min.js"></script><link rel="stylesheet" href="bootstrap-3.4.1-dist/css/bootstrap.min.css"><style>h1{color: hotpink;}</style>
</head>
<body>
<h1>第一个模板文件</h1>
</body>
</html>

"login.html"

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.7.1/jquery.min.js"></script><link rel="stylesheet" href="bootstrap-3.4.1-dist/css/bootstrap.min.css"><script src="bootstrap-3.4.1-dist/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container"><div class="row"><h1 class="text-center">登录页面</h1><form action="" method="post"><div class="form-group">用户名：<input type="text" class="form-control " name="username"></div><div class="form-group">密码：<input type="password" class="form-control " name="password"></div><div class="form-group"><input type="checkbox" name="hobby" value="a"><input type="checkbox" name="hobby" value="b"><input type="checkbox" name="hobby" value="c"></div><div class="form-group"><input type="submit" class="btn btn-success btn-block" value="登录"></div></form></div>
</div>
</body>
</html>

"userlist.html"

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.7.1/jquery.min.js"></script><link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"><script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container"><div class="row"><h1 class="text-center">用户列表</h1><a href="/add/" class="btn btn-success">添加用户</a><table class="table table-striped table-hover table-bordered"><thead><tr><th>ID</th><th>username</th><th>password</th><th>gender</th><th>action</th></tr></thead><tbody>{% for user in user_list %}<tr><td>{{ user.id }}</td><td>{{ user.username }}</td><td>{{ user.password }}</td><td>{{ user.gender }}</td><td><a href="/edit/?id={{ user.id }}" class="btn btn-success">修改</a>&nbsp;&nbsp;&nbsp;<a href="/del/?id={{ user.pk }}" class="btn btn-danger">删除</a></td></tr>{% endfor %}</tbody></table></div>
</div>
</body>
</html>

如何创建表关系(一对一一对多多对多)

### 换位思考法判断表关系
图书表和出版社表 >>> 一对多 >>> 图书表是多，出版社是一 >>> 建在多的一方
图书表和作者表 >>> 多对多 >>> 需要第三张表
作者表和作者详情表 >>> 一对一 >>> 外键字段一般建在查询频率较高的

### 在Django中如何创建表关系
"""回头复习表关系"""
class Book(models.Model):title = models.CharField(max_length=64)"""max_digits=None,:总位数decimal_places=None：小数位数"""# price decimal(8,2)price = models.DecimalField(max_digits=8, decimal_places=2)# publish_id = models.ForeignKey(to='Publish', to_field='id')"""对于外键字段关系，会自动帮我们拼接_id"""publish = models.ForeignKey(to='Publish')"""authors它是一个虚拟字段，它不会实际在表中创建出来这个字段，这一句可以自动帮助我们创建出来第三张表"""authors = models.ManyToManyField(to='Author')
"""出版社表"""
class Publish(models.Model):name = models.CharField(max_length=64)addr = models.CharField(max_length=64)
"""作者表"""
class Author(models.Model):name = models.CharField(max_length=64)author_detail = models.OneToOneField(to='AuthorDetail')
"""作者详情表"""
class AuthorDetail(models.Model):phone = models.CharField(max_length=64)email = models.CharField(max_length=64)