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055.Python前端Django模型ORM

由于前面在centos实验的过程中，pymql一直有属性错误，很难排查出问题，重新做了一个ubuntu的桌面系统同时使用pycharm开发工具作为学习开发工具，具体原因是因为在项目命名出现问题，和自己带的模块冲突，导致不能成功

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一 ORM简介

对象关系映射（Object Relational Mapping，简称ORM）。

简单的说，ORM是通过使用描述对象和数据库之间映射的元数据，将程序中的对象自动持久化到关系数据库中。ORM在业务逻辑层和数据库层之间充当了桥梁的作用。

通过一张图来介绍一下数据库与python代码之间的一个关系：

1.1 ORM特点

ORM的优点

不用写繁琐的SQL语句，用咱们熟悉的python代码，就能实现对数据的操作，提高开发效率；
可以平滑的操作，切换数据库。

ORM的缺点

ORM代码转换为SQL语句时，需要花费一定的时间，执行效率会有所降低；
长期写ORM代码，导致写SQL语句能力，会有所减弱。

1.2 改进

如果想打印orm转换过程中的sql，需要在settings中进行如下配置：

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'console':{
            'level':'DEBUG',
            'class':'logging.StreamHandler',
        },
    },
    'loggers': {
        'django.db.backends': {
            'handlers': ['console'],
            'propagate': True,
            'level':'DEBUG',
        },
    }
}　　
settings配置

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二单表操作

django使用MySQL的流程：

2.1 创建MySQL数据库

注意：ORM无法操作到数据库级别，只能操作到数据表。

安装mysql

apt-get install mysql-server mysql-common mysql-client

root@darren-virtual-machine:~# systemctl status mysql

mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: active (running) since Sun 2020-04-05 11:46:45 CST; 58s ago
 Main PID: 16219 (mysqld)
    Tasks: 27 (limit: 11869)
   CGroup: /system.slice/mysql.service
           └─16219 /usr/sbin/mysqld --daemonize --pid-file=/run/mysqld/mysqld.pid

4月 05 11:46:44 darren-virtual-machine systemd[1]: Starting MySQL Community Server...
4月 05 11:46:45 darren-virtual-machine systemd[1]: Started MySQL Community Server.

root@darren-virtual-machine:~# mysql -V

mysql  Ver 14.14 Distrib 5.7.29, for Linux (x86_64) using  EditLine wrapper

root@darren-virtual-machine:~# cat /etc/mysql/debian.cnf

# Automatically generated for Debian scripts. DO NOT TOUCH!
[client]
host     = localhost
user     = debian-sys-maint
password = gpitUmpta6ImT8hh
socket   = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
host     = localhost
user     = debian-sys-maint
password = gpitUmpta6ImT8hh
socket   = /var/run/mysqld/mysqld.sock

可以使用上面的用户名和密码，也可以直接登录

登录mysql

2.2 修改密码

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> update user set authentication_string=PASSWORD("123456")  where user='root';
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1

mysql> update user set plugin="mysql_native_password";
Query OK, 1 row affected (0.00 sec)
Rows matched: 4  Changed: 1  Warnings: 0

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> quit

2.3 登进数据库建库操作

root@darren-virtual-machine:~# mysql -uroot -p123456

mysql> create database django default charset=utf8;
Query OK, 1 row affected (0.00 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| django             |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

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三创建项目连接数据库

3.1 创建一个新的项目

root@darren-virtual-machine:~# cd /root/PycharmProjects/

root@darren-virtual-machine:~/PycharmProjects# django-admin startproject mystie

root@darren-virtual-machine:~/PycharmProjects# cd mysite/

root@darren-virtual-machine:~/PycharmProjects/mysite# tree ./*

./manage.py [error opening dir]
./mysite
├── asgi.py
├── __init__.py
├── settings.py
├── urls.py
└── wsgi.py

3.2 创建一个app应用

root@darren-virtual-machine:~/PycharmProjects/mysite# python3 manage.py startapp app01

root@darren-virtual-machine:~/PycharmProjects/mysite# vim mysite/settings.py

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'app01.apps.App01Config',
]

3.3 在settings.py里设置数据库连接

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'django',
        'HOST': '127.0.0.1',
        'PORT': 3306,
        'USER': "root",
        'PASSWORD': "123456",
    }
}

3.4 pymysql操作

root@darren-virtual-machine:~/PycharmProjects/mysite# pip3 install pymysql

Collecting pymysql
  Downloading PyMySQL-0.9.3-py2.py3-none-any.whl (47 kB)
     |████████████████████████████████| 47 kB 175 kB/s
Installing collected packages: pymysql
Successfully installed pymysql-0.9.3

3.4.1 告诉Django使用pymysql模块连接mysql数据库

root@darren-virtual-machine:~/PycharmProjects/mysite# vim mysite/__init__.py

# 在与settings.py同级目录下的__init__.py中
import pymysql
pymysql.install_as_MySQLdb()

3.4.2 创建模型（在models.py中写类）

[root@node10 pymysql]# cat app01/models.py

from django.db import models

# Create your models here.
class Book(models.Model):
        title = models.CharField(max_length=32)
        author = models.CharField(max_length=32)
        publisher = models.CharField(max_length=32)
        price = models.DecimalField(max_digits=5, decimal_places=2)
        pub_date = models.DateField()

扩展：更多字段和参数

每个字段有一些特有的参数，例如，CharField需要max_length参数来指定VARCHAR数据库字段的大小。还有一些适用于所有字段的通用参数。这些参数在文档中有详细定义，这里我们只简单介绍一些最常用的：

更多字段：

更多字段

更多参数：

更多参数

3.4.3 执行数据量迁移的命令

root@darren-virtual-machine:~/PycharmProjects/mysite# python3 manage.py makemigrations

报错如下

MySQLclient目前只支持到python3.4，因此如果使用的更高版本的python，需要修改如下：

root@darren-virtual-machine:~/PycharmProjects/mysite# vim /usr/local/lib/python3.6/dist-packages/django/db/backends/mysql/base.py

#if version < (1, 3, 13):
#    raise ImproperlyConfigured('mysqlclient 1.3.13 or newer is required; you have %s.' % Database.__version__)

注释掉就OK了。

继续执行

root@darren-virtual-machine:~/PycharmProjects/mysite# python3 manage.py makemigrations

Migrations for 'app01':
  app01/migrations/0001_initial.py
    - Create model Book

root@darren-virtual-machine:~/PycharmProjects/mysite# ll app01/migrations/

-rw-r--r-- 1 root root  739 4月   5 16:40 0001_initial.py
-rw-r--r-- 1 root root    0 4月   5 14:11 __init__.py
drwxr-xr-x 2 root root 4096 4月   5 16:40 __pycache__/

root@darren-virtual-machine:~/PycharmProjects/mysite# cat app01/migrations/0001_initial.py

# Generated by Django 3.0.5 on 2020-04-05 08:40

from django.db import migrations, models


class Migration(migrations.Migration):

    initial = True

    dependencies = [
    ]

    operations = [
        migrations.CreateModel(
            name='Book',
            fields=[
                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('title', models.CharField(max_length=32)),
                ('author', models.CharField(max_length=32)),
                ('publisher', models.CharField(max_length=32)),
                ('price', models.DecimalField(decimal_places=2, max_digits=5)),
                ('pub_date', models.DateField()),
            ],
        ),
    ]

3.4.4 迁移操作

root@darren-virtual-machine:~/PycharmProjects/mysite# python3 manage.py migrate

Operations to perform:
  Apply all migrations: admin, app01, auth, contenttypes, sessions
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying admin.0002_logentry_remove_auto_add... OK
  Applying admin.0003_logentry_add_action_flag_choices... OK
  Applying app01.0001_initial... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying auth.0007_alter_validators_add_error_messages... OK
  Applying auth.0008_alter_user_username_max_length... OK
  Applying auth.0009_alter_user_last_name_max_length... OK
  Applying auth.0010_alter_group_name_max_length... OK
  Applying auth.0011_update_proxy_permissions... OK
  Applying sessions.0001_initial... OK

查看数据库

mysql> show tables;
+----------------------------+
| Tables_in_django           |
+----------------------------+
| app01_book                 |
| auth_group                 |
| auth_group_permissions     |
| auth_permission            |
| auth_user                  |
| auth_user_groups           |
| auth_user_user_permissions |
| django_admin_log           |
| django_content_type        |
| django_migrations          |
| django_session             |
+----------------------------+
11 rows in set (0.00 sec)

mysql> desc app01_book;
+-----------+--------------+------+-----+---------+----------------+
| Field     | Type         | Null | Key | Default | Extra          |
+-----------+--------------+------+-----+---------+----------------+
| id        | int(11)      | NO   | PRI | NULL    | auto_increment |
| title     | varchar(32)  | NO   |     | NULL    |                |
| author    | varchar(32)  | NO   |     | NULL    |                |
| publisher | varchar(32)  | NO   |     | NULL    |                |
| price     | decimal(5,2) | NO   |     | NULL    |                |
| pub_date  | date         | NO   |     | NULL    |                |
+-----------+--------------+------+-----+---------+----------------+

回到顶部

四对数据库的操作　

4.1 添加表记录

配置url

root@darren-virtual-machine:~/PycharmProjects/mysite# vim mysite/urls.py

from django.contrib import admin
from django.urls import path,include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('app01/', include("app01.urls")),
]

root@darren-virtual-machine:~/PycharmProjects/mysite# vim app01/urls.py

from django.urls import path,re_path
from app01 import views
urlpatterns = [
    path('add_book/', views.add_book),
]

视图文件

root@darren-virtual-machine:~/PycharmProjects/mysite# vim app01/views.py

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

# Create your views here.
def add_book(request):
    if request.method == "GET":
        return render(request,"add_book.html")
    else:
    #方式一：通过类实例化对象的方式。注意：一定要对象.save()
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        book_obj = models.Book(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
        book_obj.save()
    return HttpResponse("新增成功")

html模板文件

创建templates目录

root@darren-virtual-machine:~/PycharmProjects/mysite# mkdir templates

注册template

root@darren-virtual-machine:~/PycharmProjects/mysite# vim mysite/settings.py

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [os.path.join(BASE_DIR,"templates")],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

root@darren-virtual-machine:~/PycharmProjects/mysite# vim templates/add_book.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h3>新增书籍</h3>
<form action="" method="post">
    {% csrf_token %}
    <p>书名：<input type="text" name="title"></p>
    <p>作者：<input type="text" name="author"></p>
    <p>出版社：<input type="text" name="publisher"></p>
    <p>价格：<input type="text" name="price"></p>
    <p>出版时间：<input type="text" name="pub_date"></p>
    <input type="submit">
</form>

</body>
</html>

访问http://127.0.0.1:8000/app01/add_book

提交

查看数据库

mysql> select * from app01_book;

+----+-----------+-----------+-----------------+--------+------------+
| id | title     | author    | publisher       | price  | pub_date   |
+----+-----------+-----------+-----------------+--------+------------+
|  1 | 红楼梦     | 曹雪芹     | 清华出版社       | 165.00  | 2018-12-12 |
+----+-----------+-----------+-----------------+--------+------------+
1 row in set (0.00 sec)

方式二：通过ORM提供的objects提供的方法 create来实现。

root@darren-virtual-machine:~/PycharmProjects/mysite# cat app01/views.py

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

# Create your views here.
def add_book(request):
    if request.method == "GET":
        return render(request,"add_book.html")
    else:
    #方式一：
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        #book_obj = models.Book(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
        #book_obj.save()
    #方式二，推荐使用
        book_obj = models.Book.objects.create(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)

访问插入数据http://127.0.0.1:8000/app01/add_book

数据库查看记录

mysql> select * from app01_book;

+----+--------------+-----------+-----------------+--------+------------+
| id | title        | author    | publisher       | price  | pub_date   |
+----+--------------+-----------+-----------------+--------+------------+
|  1 | 红楼梦        | 曹雪芹     | 清华出版社        | 165.00 | 2018-12-12 |
|  2 | 三国演义      | 罗贯中     | 北大出版社        | 199.00 | 2018-12-23 |
+----+--------------+-----------+-----------------+--------+------------+

4.2 查询操作

4.2.1 查询API

<1> all():                  查询所有结果   　　
<2> filter(**kwargs):       它包含了与所给筛选条件相匹配的对象
<3> get(**kwargs):          返回与所给筛选条件相匹配的对象，返回结果有且只有一个，                            如果符合筛选条件的对象超过一个或者没有都会抛出错误。 
<4> exclude(**kwargs):      它包含了与所给筛选条件不匹配的对象 
<5> order_by(*field):       对查询结果排序
<6> reverse():              对查询结果反向排序 
<7> count():                返回数据库中匹配查询(QuerySet)的对象数量。  
<8> first():                返回第一条记录  
<9> last():                返回最后一条记录  
<10> exists():              如果QuerySet包含数据，就返回True，否则返回False 
<11> values(*field):        返回一个ValueQuerySet——一个特殊的QuerySet，运行后得到的并不是一系列                            model的实例化对象，而是一个可迭代的字典序列
<12> values_list(*field):   它与values()非常相似，它返回的是一个元组序列，values返回的是一个字典序列 
<13> distinct():            从返回结果中剔除重复纪录

4.2.2 基于双下划线的模糊查询

Book.objects.filter(price__in=[100,200,300])
Book.objects.filter(price__gt=100)
Book.objects.filter(price__lt=100)
Book.objects.filter(price__range=[100,200])
Book.objects.filter(title__contains="法")
Book.objects.filter(title__icontains="python")  # 不区分大小写
Book.objects.filter(title__startswith="九")
Book.objects.filter(pub_date__year=2018)

4.2.3 实例

添加测试数据

root@darren-virtual-machine:~/PycharmProjects/mysite# cat app01/views.py

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

# Create your views here.
def add_book(request):
    if request.method == "GET":
        return render(request,"add_book.html")
    else:
    #方式一：
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        #book_obj = models.Book(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
        #book_obj.save()
    #方式二，推荐使用
        #book_obj = models.Book.objects.create(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
        #添加数据，添加完成后，及时删除
        models.Book.objects.create(title="水浒传",author="施耐庵",price=180, publisher="北电出版社", pub_date="2019-1-12")
        models.Book.objects.create(title="西游记",author="吴承恩",price=185, publisher="北大出版社", pub_date="2019-2-12")
        models.Book.objects.create(title="独孤九剑", author="风清扬",price = 190, publisher = "华山出版社", pub_date = "2019-1-15")
        models.Book.objects.create(title="葵花宝典", author="东方不败", price=120, publisher="黑木崖出版社", pub_date="2019-1-20")
        models.Book.objects.create(title="易筋经", author="方丈大师", price=140, publisher="少林出版社", pub_date="2019-1-23")
        models.Book.objects.create(title="道德经", author="老子", price=176, publisher="北大出版社", pub_date="2019-2-23")
        models.Book.objects.create(title="论语", author="孔子弟子", price=165, publisher="北电出版社", pub_date="2019-2-13")
        models.Book.objects.create(title="九阳神功", author="张无忌", price=130, publisher="少林出版社", pub_date="2018-1-23")
        models.Book.objects.create(title="九阴真经", author="黄裳", price=145, publisher="大宋出版社", pub_date="2017-3-23")
    return HttpResponse("新增成功")

访问http://127.0.0.1:8000/app01/add_book，点击submit

查看数据库

mysql> select * from app01_book;

mysql> select * from app01_book;
+----+--------------+--------------+--------------------+--------+------------+
| id | title        | author       | publisher          | price  | pub_date   |
+----+--------------+--------------+--------------------+--------+------------+
|  1 | 红楼梦       | 曹雪芹       | 清华出版社         | 165.00 | 2018-12-12 |
|  2 | 三国演义     | 罗贯中       | 北大出版社         | 199.00 | 2018-12-23 |
|  3 | 水浒传       | 施耐庵       | 北电出版社         | 180.00 | 2019-01-12 |
|  4 | 西游记       | 吴承恩       | 北大出版社         | 185.00 | 2019-02-12 |
|  5 | 独孤九剑     | 风清扬       | 华山出版社         | 190.00 | 2019-01-15 |
|  6 | 葵花宝典     | 东方不败     | 黑木崖出版社       | 120.00 | 2019-01-20 |
|  7 | 易筋经       | 方丈大师     | 少林出版社         | 140.00 | 2019-01-23 |
|  8 | 道德经       | 老子         | 北大出版社         | 176.00 | 2019-02-23 |
|  9 | 论语         | 孔子弟子     | 北电出版社         | 165.00 | 2019-02-13 |
| 10 | 九阳神功     | 张无忌       | 少林出版社         | 130.00 | 2018-01-23 |
| 11 | 九阴真经     | 黄裳         | 大宋出版社         | 145.00 | 2017-03-23 |
+----+--------------+--------------+--------------------+--------+------------+

必须恢复views.py，否则会重复添加

编辑路由

root@darren-virtual-machine:~/PycharmProjects/mysite# cat app01/urls.py

from django.urls import path,re_path
from app01 import views
urlpatterns = [
    path('add_book/', views.add_book),
    path('query_book',views.query_book),
]

定义视图函数

root@darren-virtual-machine:~/PycharmProjects/mysite# cat app01/views.py

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

# Create your views here.
def add_book(request):
    if request.method == "GET":
        return render(request,"add_book.html")
    else:
    #方式一：
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        #book_obj = models.Book(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
        #book_obj.save()
    #方式二，推荐使用
        book_obj = models.Book.objects.create(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
    return HttpResponse("新增成功")
def query_book(request):
    #all，获取所有结果
    books = models.Book.objects.all()
    print(books)

    return HttpResponse("查询成功")

访问http://127.0.0.1:8000/app01/query_book

输出结果

[05/Apr/2020 11:59:21] "GET /app01/add_book/ HTTP/1.1" 200 618
<QuerySet [<Book: Book object (1)>, <Book: Book object (2)>, <Book: Book object (3)>, <Book: Book object (4)>, <Book: Book object (5)>, <Book: Book object (6)>, <Book: Book object (7)>, <Book: Book object (8)>, <Book: Book object (9)>, <Book: Book object (10)>, <Book: Book object (11)>]>
[05/Apr/2020 11:59:26] "GET /app01/query_book HTTP/1.1" 200 12

model返回一个title值

root@darren-virtual-machine:~/PycharmProjects/mysite# cat app01/models.py

from django.db import models

# Create your models here.
class Book(models.Model):
        title = models.CharField(max_length=32)
        author = models.CharField(max_length=32)
        publisher = models.CharField(max_length=32)
        price = models.DecimalField(max_digits=5, decimal_places=2)
        pub_date = models.DateField()
        def __str__(self):
                return self.title

再次访问查看

[05/Apr/2020 12:04:48] "GET /app01/query_book HTTP/1.1" 200 12
<QuerySet [<Book: 红楼梦>, <Book: 三国演义>, <Book: 水浒传>, <Book: 西游记>, <Book: 独孤九剑>, <Book: 葵花宝典>, <Book: 易筋经>, <Book: 道德经>, <Book: 论语>, <Book: 九阳神功>, <Book: 九阴真经>]>

root@darren-virtual-machine:~/PycharmProjects/mysite# cat app01/views.py

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

# Create your views here.
def add_book(request):
    if request.method == "GET":
        return render(request,"add_book.html")
    else:
    #方式一：
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        #book_obj = models.Book(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
        #book_obj.save()
    #方式二，推荐使用
        book_obj = models.Book.objects.create(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
    return HttpResponse("新增成功")
def query_book(request):
    #filter Query 对象，类似于列表，获取满足条件的对象，filter可以满足多个条件，之间关系为and
    books_filter = models.Book.objects.filter(pk=3)
    print(books_filter)
    #get,获取对象，没有结果或者有多个结果 会报错
    books_get = models.Book.objects.get(pk=3)
    print(books_get,type(books_get))
    #exclude，query类型，和filter相反，排除满足条件的类型
    books_exclude = models.Book.objects.exclude(pk=3)
    print(books_exclude)
    #order_by默认升序，降序前面添加-即可
    books_order_by = models.Book.objects.order_by("price")
    print(books_order_by)
    books_order_by = models.Book.objects.order_by("-price")
    print(books_order_by)
    #reverse
    books_reverse = models.Book.objects.order_by("-price").reverse()
    print(books_reverse)
    #first获取第一条
    book_first= models.Book.objects.filter(pk=4).first()
    print(book_first)
    #exist判断结果是否讯在，存在返回true
    books_exist = models.Book.objects.exclude(pk=4)
    print(books_exist,type(books_exist))
    #vaules,QUeryset类型，类似于字典
    books_vaules = models.Book.objects.values("title","price")
    print(books_vaules,type(books_vaules))
    # vaules_list,QUeryset类型，类似于元祖
    books_vaules1 = models.Book.objects.values_list("title","price")
    print(books_vaules1,type(books_vaules1))
    #distinct,去除重复
    books = models.Book.objects.values("publisher").distinct()
    print(books,type(books))

    return HttpResponse("查询成功")

查询结果

<QuerySet [<Book: 水浒传>]>
水浒传 <class 'app01.models.Book'>
<QuerySet [<Book: 红楼梦>, <Book: 三国演义>, <Book: 西游记>, <Book: 独孤九剑>, <Book: 葵花宝典>, <Book: 易筋经>, <Book: 道德经>, <Book: 论语>, <Book: 九阳神功>, <Book: 九阴真经>]>
<QuerySet [<Book: 葵花宝典>, <Book: 九阳神功>, <Book: 易筋经>, <Book: 九阴真经>, <Book: 红楼梦>, <Book: 论语>, <Book: 道德经>, <Book: 水浒传>, <Book: 西游记>, <Book: 独孤九剑>, <Book: 三国演义>]>
<QuerySet [<Book: 三国演义>, <Book: 独孤九剑>, <Book: 西游记>, <Book: 水浒传>, <Book: 道德经>, <Book: 红楼梦>, <Book: 论语>, <Book: 九阴真经>, <Book: 易筋经>, <Book: 九阳神功>, <Book: 葵花宝典>]>
<QuerySet [<Book: 葵花宝典>, <Book: 九阳神功>, <Book: 易筋经>, <Book: 九阴真经>, <Book: 红楼梦>, <Book: 论语>, <Book: 道德经>, <Book: 水浒传>, <Book: 西游记>, <Book: 独孤九剑>, <Book: 三国演义>]>
西游记
<QuerySet [<Book: 红楼梦>, <Book: 三国演义>, <Book: 水浒传>, <Book: 独孤九剑>, <Book: 葵花宝典>, <Book: 易筋经>, <Book: 道德经>, <Book: 论语>, <Book: 九阳神功>, <Book: 九阴真经>]> <class 'django.db.models.query.QuerySet'>
<QuerySet [{'title': '红楼梦', 'price': Decimal('165.00')}, {'title': '三国演义', 'price': Decimal('199.00')}, {'title': '水浒传', 'price': Decimal('180.00')}, {'title': '西游记', 'price': Decimal('185.00')}, {'title': '独孤九剑', 'price': Decimal('190.00')}, {'title': '葵花宝典', 'price': Decimal('120.00')}, {'title': '易筋经', 'price': Decimal('140.00')}, {'title': '道德经', 'price': Decimal('176.00')}, {'title': '论语', 'price': Decimal('165.00')}, {'title': '九阳神功', 'price': Decimal('130.00')}, {'title': '九阴真经', 'price': Decimal('145.00')}]> <class 'django.db.models.query.QuerySet'>
<QuerySet [('红楼梦', Decimal('165.00')), ('三国演义', Decimal('199.00')), ('水浒传', Decimal('180.00')), ('西游记', Decimal('185.00')), ('独孤九剑', Decimal('190.00')), ('葵花宝典', Decimal('120.00')), ('易筋经', Decimal('140.00')), ('道德经', Decimal('176.00')), ('论语', Decimal('165.00')), ('九阳神功', Decimal('130.00')), ('九阴真经', Decimal('145.00'))]> <class 'django.db.models.query.QuerySet'>
<QuerySet [{'publisher': '清华出版社'}, {'publisher': '北大出版社'}, {'publisher': '北电出版社'}, {'publisher': '华山出版社'}, {'publisher': '黑木崖出版社'}, {'publisher': '少林出版社'}, {'publisher': '大宋出版社'}]> <class 'django.db.models.query.QuerySet'>
[05/Apr/2020 12:37:56] "GET /app01/query_book HTTP/1.1" 200 1

4.3 删除记录

删除方法就是 delete()。它运行时立即删除对象而不返回任何值。例如：

model_obj.delete()

你也可以一次性删除多个对象。每个 QuerySet 都有一个 delete() 方法，它一次性删除 QuerySet 中所有的对象。

例如，下面的代码将删除 pub_date 是2018年的 Book 对象：

Book.objects.filter(pub_date__year=2018).delete()

设计url

from django.urls import path,re_path
from app01 import views
urlpatterns = [
    path('add_book/', views.add_book),    #新增操作
    path('query_book/',views.query_book), #查询错做
    path('del_book/',views.del_book)      #删除操作
]

视图函数

root@darren-virtual-machine:~/PycharmProjects/mysite# cat app01/views.py

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

# Create your views here.
def add_book(request):
    if request.method == "GET":
        return render(request,"add_book.html")
    else:
    #方式一：
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        #book_obj = models.Book(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
        #book_obj.save()
    #方式二，推荐使用
        book_obj = models.Book.objects.create(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
    return HttpResponse("新增成功")
def query_book(request):
    #基于双线划线的模糊查询
    books = models.Book.objects.filter(price_in=[120,160,150])
    print(books)
    books = models.Book.objects.filter(price_range=[120, 160])
    print(books)

    return HttpResponse("查询成功")

def del_book(request):
    pk = request.GET.get('pk')
    print(pk)
    #方式一使用对象的形式删除
    book_obj = models.Book.objects.filter(pk=pk).first()
    book_obj.delete()
    return HttpResponse("删除成功")

访问http://127.0.0.1:8000/app01/del_book/?pk=3

查看数据库

mysql> select * from app01_book;

+----+--------------+--------------+--------------------+--------+------------+
| id | title        | author       | publisher          | price  | pub_date   |
+----+--------------+--------------+--------------------+--------+------------+
|  1 | 红楼梦       | 曹雪芹       | 清华出版社         | 165.00 | 2018-12-12 |
|  2 | 三国演义     | 罗贯中       | 北大出版社         | 199.00 | 2018-12-23 |
|  4 | 西游记       | 吴承恩       | 北大出版社         | 185.00 | 2019-02-12 |
|  5 | 独孤九剑     | 风清扬       | 华山出版社         | 190.00 | 2019-01-15 |
|  6 | 葵花宝典     | 东方不败     | 黑木崖出版社       | 120.00 | 2019-01-20 |
|  7 | 易筋经       | 方丈大师     | 少林出版社         | 140.00 | 2019-01-23 |
|  8 | 道德经       | 老子         | 北大出版社         | 176.00 | 2019-02-23 |
|  9 | 论语         | 孔子弟子     | 北电出版社         | 165.00 | 2019-02-13 |
| 10 | 九阳神功     | 张无忌       | 少林出版社         | 130.00 | 2018-01-23 |
| 11 | 九阴真经     | 黄裳         | 大宋出版社         | 145.00 | 2017-03-23 |
+----+--------------+--------------+--------------------+--------+------------+

方法二

视图函数

root@darren-virtual-machine:~/PycharmProjects/mysite# cat app01/views.py

。。。。。。

def del_book(request):
    pk = request.GET.get('pk')
    print(pk)
    #方式一使用对象的形式删除
    #book_obj = models.Book.objects.filter(pk=pk).first()
    #book_obj.delete()
    #方式二
    books = models.Book.objects.filter(pk=pk).delete()      #返回值是受影响的行数
    print(books)
    return HttpResponse("删除成功"

在 Django 删除对象时，会模仿 SQL 约束 ON DELETE CASCADE 的行为，换句话说，删除一个对象时也会删除与它相关联的外键对象。例如：

b = Book.objects.get(pk=1)
# This will delete the Blog and all of its Entry objects.
b.delete()

要注意的是： delete() 方法是 QuerySet 上的方法，但并不适用于 Manager 本身。这是一种保护机制，是为了避免意外地调用 Entry.objects.delete() 方法导致所有的记录被误删除。如果你确认要删除所有的对象，那么你必须显式地调用：

Book.objects.all().delete()

访问http://127.0.0.1:8000/app01/del_book/?pk=4

mysql> select * from app01_book;

+----+--------------+--------------+--------------------+--------+------------+
| id | title        | author       | publisher          | price  | pub_date   |
+----+--------------+--------------+--------------------+--------+------------+
|  1 | 红楼梦       | 曹雪芹       | 清华出版社         | 165.00 | 2018-12-12 |
|  2 | 三国演义     | 罗贯中       | 北大出版社         | 199.00 | 2018-12-23 |
|  5 | 独孤九剑     | 风清扬       | 华山出版社         | 190.00 | 2019-01-15 |
|  6 | 葵花宝典     | 东方不败     | 黑木崖出版社       | 120.00 | 2019-01-20 |
|  7 | 易筋经       | 方丈大师     | 少林出版社         | 140.00 | 2019-01-23 |
|  8 | 道德经       | 老子         | 北大出版社         | 176.00 | 2019-02-23 |
|  9 | 论语         | 孔子弟子     | 北电出版社         | 165.00 | 2019-02-13 |
| 10 | 九阳神功     | 张无忌       | 少林出版社         | 130.00 | 2018-01-23 |
| 11 | 九阴真经     | 黄裳         | 大宋出版社         | 145.00 | 2017-03-23 |
+----+--------------+--------------+--------------------+--------+------------+

调试输出

4
(1, {'app01.Book': 1})
[05/Apr/2020 13:26:15] "GET /app01/del_book/?pk=4 HTTP/1.1" 200 12

4.4 修改表记录

设计url

from django.urls import path,re_path
from app01 import views
urlpatterns = [
    path('add_book/', views.add_book),    #新增操作
    path('query_book/',views.query_book), #查询错做
    path('del_book/',views.del_book),     #删除操作
    path('edit_book/',views.edit_book),    #编辑操作
]

视图函数

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

# Create your views here.
def add_book(request):
    if request.method == "GET":
        return render(request,"add_book.html")
    else:
    #方式一：
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        #book_obj = models.Book(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
        #book_obj.save()
    #方式二，推荐使用
        book_obj = models.Book.objects.create(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
    return HttpResponse("新增成功")
def query_book(request):
    #基于双线划线的模糊查询
    books = models.Book.objects.filter(price_in=[120,160,150])
    print(books)
    books = models.Book.objects.filter(price_range=[120, 160])
    print(books)

    return HttpResponse("查询成功")

def del_book(request):
    pk = request.GET.get('pk')
    print(pk)
    #方式一使用对象的形式删除
    #book_obj = models.Book.objects.filter(pk=pk).first()
    #book_obj.delete()
    #方式二
    books = models.Book.objects.filter(pk=pk).delete()
    print(books)
    return HttpResponse("删除成功")

def edit_book(request):
    pk = request.GET.get("pk")
    if request.method == "GET":
        book_obj = models.Book.objects.filter(pk=pk).first()
        return render(request,"edit_book.html",{"book_obj":book_obj})

html模板文件

root@darren-virtual-machine:~/PycharmProjects/mysite# cat templates/edit_book.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h3>编辑数据</h3>

<form action="" method="post">
    {% csrf_token %}
    <p>书名：<input type="text" name="title" value="{{ book_obj.title }}"></p>
    <p>作者：<input type="text" name="author" value="{{ book_obj.author }}"></p>
    <p>出版社：<input type="text" name="publisher" value="{{ book_obj.publisher }}"></p>
    <p>价格：<input type="text" name="price" value="{{ book_obj.price }}"></p>
    <p>出版时间：<input type="text" name="pub_date" value="{{ book_obj.pub_date|date:"Y-m-d" }}"></p>
    <input type="submit">
</form>

</body>
</html>

访问http://127.0.0.1:8000/app01/edit_book/?pk=5

修改显示时间

<form action="" method="post">
    {% csrf_token %}
    <p>书名：<input type="text" name="title" value="{{ book_obj.title }}"></p>
    <p>作者：<input type="text" name="author" value="{{ book_obj.author }}"></p>
    <p>出版社：<input type="text" name="publisher" value="{{ book_obj.publisher }}"></p>
    <p>价格：<input type="text" name="price" value="{{ book_obj.price }}"></p>
    <p>出版时间：<input type="text" name="pub_date" value="{{ book_obj.pub_date|date:"Y-m-d" }}"></p>
    <input type="submit">
</form>

刷新

编辑操作

方式一：

通过修改实例对象的属性方式。注意：一定要对象.save()

def edit_book(request):
    pk = request.GET.get("pk")
    if request.method == "GET":
        book_obj = models.Book.objects.filter(pk=pk).first()
        return render(request,"edit_book.html",{"book_obj":book_obj})
    else:
    #方式一：
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        book_obj = models.Book.objects.filter(pk=pk).first()
        book_obj.price = price
        book_obj.save()
    return HttpResponse("编辑成功")

访问http://127.0.0.1:8000/app01/edit_book/?pk=5并修改

数据库查询

+----+--------------+--------------+--------------------+--------+------------+
| id | title        | author       | publisher          | price  | pub_date   |
+----+--------------+--------------+--------------------+--------+------------+
|  1 | 红楼梦       | 曹雪芹       | 清华出版社         | 165.00 | 2018-12-12 |
|  2 | 三国演义     | 罗贯中       | 北大出版社         | 199.00 | 2018-12-23 |
|  5 | 独孤九剑     | 风清扬       | 华山出版社         | 143.00 | 2019-01-15 |
|  6 | 葵花宝典     | 东方不败     | 黑木崖出版社       | 120.00 | 2019-01-20 |
|  7 | 易筋经       | 方丈大师     | 少林出版社         | 140.00 | 2019-01-23 |
|  8 | 道德经       | 老子         | 北大出版社         | 176.00 | 2019-02-23 |
|  9 | 论语         | 孔子弟子     | 北电出版社         | 165.00 | 2019-02-13 |
| 10 | 九阳神功     | 张无忌       | 少林出版社         | 130.00 | 2018-01-23 |
| 11 | 九阴真经     | 黄裳         | 大宋出版社         | 145.00 | 2017-03-23 |
+----+--------------+--------------+--------------------+--------+------------+

方式二：

通过ORM提供的objects提供的方法 update来实现。

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

# Create your views here.
def add_book(request):
    if request.method == "GET":
        return render(request,"add_book.html")
    else:
    #方式一：
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        #book_obj = models.Book(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
        #book_obj.save()
    #方式二，推荐使用
        book_obj = models.Book.objects.create(title=title,author=author,publisher=publisher,price=price,pub_date=pub_date)
    return HttpResponse("新增成功")
def query_book(request):
    #基于双线划线的模糊查询
    books = models.Book.objects.filter(price_in=[120,160,150])
    print(books)
    books = models.Book.objects.filter(price_range=[120, 160])
    print(books)

    return HttpResponse("查询成功")

def del_book(request):
    pk = request.GET.get('pk')
    print(pk)
    #方式一使用对象的形式删除
    #book_obj = models.Book.objects.filter(pk=pk).first()
    #book_obj.delete()
    #方式二
    books = models.Book.objects.filter(pk=pk).delete()
    print(books)
    return HttpResponse("删除成功")

def edit_book(request):
    pk = request.GET.get("pk")
    if request.method == "GET":
        book_obj = models.Book.objects.filter(pk=pk).first()
        return render(request,"edit_book.html",{"book_obj":book_obj})
    else:
    #方式二：
        title = request.POST.get("title")
        author = request.POST.get("author")
        publisher = request.POST.get("publisher")
        price = request.POST.get("price")
        pub_date = request.POST.get("pub_date")
        books = models.Book.objects.filter(pk=pk).update(price=price)    #返回影响事物的行数
        print(books)
    return HttpResponse("编辑成功")

此外，update()方法对于任何结果集（QuerySet）均有效，这意味着你可以同时更新多条记录update()方法会返回一个整型数值，表示受影响的记录条数。

访问 http://127.0.0.1:8000/app01/edit_book/?pk=6并修改

查看数据库

mysql> select * from app01_book;
+----+--------------+--------------+--------------------+--------+------------+
| id | title        | author       | publisher          | price  | pub_date   |
+----+--------------+--------------+--------------------+--------+------------+
|  1 | 红楼梦       | 曹雪芹       | 清华出版社         | 165.00 | 2018-12-12 |
|  2 | 三国演义     | 罗贯中       | 北大出版社         | 199.00 | 2018-12-23 |
|  5 | 独孤九剑     | 风清扬       | 华山出版社         | 143.00 | 2019-01-15 |
|  6 | 葵花宝典     | 东方不败     | 黑木崖出版社       | 179.00 | 2019-01-20 |
|  7 | 易筋经       | 方丈大师     | 少林出版社         | 140.00 | 2019-01-23 |
|  8 | 道德经       | 老子         | 北大出版社         | 176.00 | 2019-02-23 |
|  9 | 论语         | 孔子弟子     | 北电出版社         | 165.00 | 2019-02-13 |
| 10 | 九阳神功     | 张无忌       | 少林出版社         | 130.00 | 2018-01-23 |
| 11 | 九阴真经     | 黄裳         | 大宋出版社         | 145.00 | 2017-03-23 |
+----+--------------+--------------+--------------------+--------+------------+

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学习记录，小白一枚

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原文地址：https://www.cnblogs.com/wangsirde0428/p/14322878.html

055.Python前端Django模型ORM

一 ORM简介

1.1 ORM特点

1.2 改进

二 单表操作

2.1 创建MySQL数据库

2.2 修改密码

2.3 登进数据库建库操作

三 创建项目连接数据库

3.1 创建一个新的项目

3.2 创建一个app应用

3.3 在settings.py里设置数据库连接

3.4 pymysql操作

3.4.1 告诉Django使用pymysql模块连接mysql数据库

3.4.2 创建模型（在models.py中写类）

3.4.3 执行数据量迁移的命令

3.4.4 迁移操作

四 对数据库的操作

4.1 添加表记录

4.2 查询操作

4.2.1 查询API

4.2.2 基于双下划线的模糊查询

4.2.3 实例

4.3 删除记录

4.4 修改表记录

二单表操作

三创建项目连接数据库

四对数据库的操作　