一、表字段的增删改查  

• 新增

from django.db import models# Create your models here.class User(models.Model):    id = models.AutoField(primary_key=True)    name = models.CharField(max_length=32)    pwd = models.CharField(max_length=32)    addr= models.CharField(max_length=64)    # 新增addr字段

注意：对于已存在数据的表，新增字段必须要给定默认值，默认值有两种方法

如果models.py里没有指定默认值，执行python3  manage.py makemigrations时，会提示以下信息

 

'''D:\code\mylogin>python3 manage.py makemigrationsYou are trying to add a non-nullable field 'addr' to user without a default; we can't do that (the database needs something to populate existing rows).Please select a fix: 1) Provide a one-off default now (will be set on all existing rows with a null value for this column) 2) Quit, and let me add a default in models.py'''

 

选择1，就是在makemigrations时添加新字段的默认值

Select an option: 1Please enter the default value now, as valid PythonThe datetime and django.utils.timezone modules are available, so you can do e.g. timezone.nowType 'exit' to exit this prompt>>> 'shanghai'Migrations for 'app01':  app01\migrations\0002_user_addr.py    - Add field addr to userD:\code\mylogin>python3 manage.py migrateOperations to perform:  Apply all migrations: admin, app01, auth, contenttypes, sessionsRunning migrations:  Applying app01.0002_user_addr... OK

在models.py里指定新字段的默认值

from django.db import models# Create your models here.class User(models.Model):    id = models.AutoField(primary_key=True)    name = models.CharField(max_length=32)    pwd = models.CharField(max_length=32)    addr= models.CharField(max_length=64)    phone=models.CharField(max_length=11,default='')

• 修改字段

from django.db import models# Create your models here.class User(models.Model):    id = models.AutoField(primary_key=True)    name = models.CharField(max_length=32)    pwd = models.CharField(max_length=32)    addr= models.CharField(max_length=128)      # max_length=64改为28    phone_num=models.CharField(max_length=11,default='')          # phone 改为phone_num

D:\code\mylogin>python3 manage.py makemigrationsDid you rename user.phone to user.phone_num (a CharField)? [y/N] y                 # 对于已上线的项目 谨慎做修改字段名的操作Migrations for 'app01':  app01\migrations\0004_auto_20190312_1403.py    - Rename field phone on user to phone_num    - Alter field addr on userD:\code\mylogin>python3 manage.py migrateOperations to perform:  Apply all migrations: admin, app01, auth, contenttypes, sessionsRunning migrations:  Applying app01.0004_auto_20190312_1403... OK

• 删除字段(同理，对于已上线的项目，删除字段慎之又慎，别给自己找麻烦)

from django.db import models# Create your models here.class User(models.Model):    id = models.AutoField(primary_key=True)    name = models.CharField(max_length=32)    pwd = models.CharField(max_length=32)    addr= models.CharField(max_length=128)    # phone_num=models.CharField(max_length=11,default='')      # 注释就是删除

D:\code\mylogin>python3 manage.py makemigrationsMigrations for 'app01':  app01\migrations\0005_remove_user_phone_num.py    - Remove field phone_num from userD:\code\mylogin>python3 manage.py migrateOperations to perform:  Apply all migrations: admin, app01, auth, contenttypes, sessionsRunning migrations:  Applying app01.0005_remove_user_phone_num... OK

二、单表数据增删改查 

• 查询单条数据  user = models.User.objects.filter(name=name, pwd=pwd).first() 
• 返回的是user对象，可以通过user.name得到属性的值

def login(request):    if request.method == 'GET':        return render(request, 'login.html')    else:        # 取出POST中携带的参数        name = request.POST.get('name')        pwd = request.POST.get('pwd')        if name and pwd:            # 去数据库里查            user = models.User.objects.filter(name=name, pwd=pwd).first()            # print(user.name,user.pwd)  # user是一个实例对象  对象.属性 可获取到属性的值            if user:  # user有值的情况                return redirect('https://www.baidu.com')            else:                return HttpResponse('用户名或密码错误')        else:            return HttpResponse('用户名或密码不能为空')

• 查询所有数据  ret = models.User.objects.all()
• 返回的是QuerySet对象 [<User: User object (1)>, <User: User object (2)>]
• 通过render渲染，返回给前台展示   return render(request, 'userlist.html', {'userlist': ret})

def userlist(request):    # 查出 User表中的所有数据    # sql: select * from app01_user;    ret = models.User.objects.all()  # orm返回一个QuerySet对象django.db.models.query.QuerySet    return render(request, 'userlist.html', {
    'userlist': ret})

    
              
      
    新增用户
              
      
      
            {% for user in userlist %}        
    {% endfor %}    
           
        
                     
id
                     
name
                     
pwd
                     
addr
                     
操作
                
               
       
        
                     
{
    { user.id }}
                     
{
    { user.name }}
                     
{
    { user.pwd }}
                     
{
    { user.addr }}
                     
                修改                删除                修改            
                
       
      

• 删除记录  先通过filter方法查出数据，再调delete方法删除之   models.User.objects.filter(id=id).delete()
• 返回的是：影响的行数
• 前端可通过get携带参数    <a href="/userdel?id={
  { user.id }}">删除</a>

def userdel(request):    # 取出前端传过来的id    id = request.GET.get('id')    ret = models.User.objects.filter(id=id).delete()    print(ret, type(ret))    return redirect('/userlist/')

• 新增数据 
• 方式1：models.User.objects.create(name=name, pwd=pwd, addr=addr)     # 调用create()方法创建一条新纪录
• 方式2：models.User(name=name, pwd=pwd, addr=addr).save()   # 先生成一个新的user对象，再调save方法保存到数据库
• 前端的form表单中的数据在post到后端时，将form表单的数据以key=value&key=value的格式打包到body里：name=lck&pwd=1234  可通过request.body拿到

def useradd(request):    if request.method == 'GET':        return render(request, 'useradd.html')    elif request.method == 'POST':        name = request.POST.get('name')        pwd = request.POST.get('pwd')        addr = request.POST.get('addr')        if name and pwd and addr:            # 方式1: create()方法创建一条新纪录            # models.User.objects.create(name=name, pwd=pwd, addr=addr)            # 方式2: 先生成一个新的user对象，再调save方法保存到数据库            models.User(name=name, pwd=pwd, addr=addr).save()            return redirect('/userlist/')        else:            return HttpResponse('用户名、密码、地址不能为空')

    
              
      
      
    
       
        
        用户名        
            
       
    
       
        
        密码        
            
       
    
       
        
        地址        
            
       
    
       提交
      

• 修改数据   models.User.objects.filter(id=id).update(name=name,pwd=pwd,addr=addr)  # 先通过前端get携带的id，调用filter方法查出对应数据，再调update方法更新
• 返回的是：影响的行数
• 后端逻辑：前端GET携带id请求，后端返回此id对应的数据，前端修改后POST提交到后端，后端完成数据更新

def useredit(request):    if request.method == 'GET':        id=request.GET.get('id')        user=models.User.objects.filter(id=id).first()        return render(request,'useredit.html',{
    'user':user})    else:        id=request.GET.get('id')  # 前端form的action的url里带了id 所以可以从GET里取出        id1=request.POST.get('id') # 前端form表单里id隐藏了，所以亦可以从POST里取出        name=request.POST.get('name')        pwd=request.POST.get('pwd')        addr=request.POST.get('addr')        # user=models.User.objects.filter(id=id)  # 查出id对应的数据，然后update新数据        # user.update(name=name,pwd=pwd,addr=addr)        # 上面两行可以合并成一行        models.User.objects.filter(id=id).update(name=name,pwd=pwd,addr=addr)        return redirect('/userlist/')

    
              
      
修改用户信息
      
    
       
        
                
        
用户名: 
        
        
密码: 
        
        
地址: