07 -模型层ORM

1、orm简介

2、

models.py

from django.db import models

# Create your models here.

class Book(models.Model):
    id = models.AutoField(primary_key=True)
    title = models.CharField(max_length=32, unique=True)
    state = models.BooleanField()
    pub_date = models.DateField()
    price = models.DecimalField(max_digits=8, decimal_places=2)   # 999999.00
    publish = models.CharField(max_length=22)                     # 10000000.00  溢出

C:\Windows\system32>mysql -uroot -proot

mysql> create database orm;      # 创建orm数据库
Query OK, 1 row affected (0.00 sec)

settings默认sqlite3数据库

设置database为mysql

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'orm',            # 要连接的数据库，连接前需要创建好
        'USER': 'root',           # 连接数据库的用户名
        'PASSWORD': 'root',          # 连接数据库的密码
        'HOST': '127.0.0.1',     # 连接主机，默认本级
        'PORT': 3306,            # 端口 默认3306
    }
}

　　（3）django调用的是pymysql

报错：

E:\PycharmProjects\cnblog>python manage.py makemigrations
Traceback (most recent call last):
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\backends\mysql\base.py", line , in <module>
    import MySQLdb as Database
ModuleNotFoundError: No module named 'MySQLdb'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "manage.py", line , in <module>
    execute_from_command_line(sys.argv)
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\management\__init__.py", line , in execute_from_command_line
    utility.execute()
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\management\__init__.py", line , in execute
    django.setup()
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\__init__.py", line , in setup
    apps.populate(settings.INSTALLED_APPS)
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\apps\registry.py", line , in populate
    app_config.import_models()
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\apps\config.py", line , in import_models
    self.models_module = import_module(models_module_name)
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\importlib\__init__.py", line , in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line , in _gcd_import
  File "<frozen importlib._bootstrap>", line , in _find_and_load
  File "<frozen importlib._bootstrap>", line , in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line , in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line , in exec_module
  File "<frozen importlib._bootstrap>", line , in _call_with_frames_removed
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\contrib\auth\models.py", line , in <module>
    from django.contrib.auth.base_user import AbstractBaseUser, BaseUserManager
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\contrib\auth\base_user.py", line , in <module>
    class AbstractBaseUser(models.Model):
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\base.py", line , in __new__
    new_class.add_to_class('_meta', Options(meta, app_label))
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\base.py", line , in add_to_class
    value.contribute_to_class(cls, name)
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\options.py", line , in contribute_to_class
    self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\__init__.py", line , in __getattr__
    return getattr(connections[DEFAULT_DB_ALIAS], item)
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\utils.py", line , in __getitem__
    backend = load_backend(db['ENGINE'])
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\utils.py", line , in load_backend
    return import_module('%s.base' % backend_name)
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\importlib\__init__.py", line , in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "C:\Users\Venicid\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\backends\mysql\base.py", line , in <module>
    ) from err
django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module.

解决：

__init__.py

import pymysql

pymysql.install_as_MySQLdb()

注意2:确保配置文件中的INSTALLED_APPS中写入我们创建的app名称

注意3：如果报错的话

django.core.exceptions.ImproperlyConfigured: mysqlclient 1.3.3 or newer is required; you have 0.7.11.None

　　

注意4: 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',
        },
    }
}　　

最后通过两条数据库迁移命令即可在指定的数据库中创建表 ：

python manage.py makemigrations
python manage.py migrate

插入数据，创建表

3、单表操作之添加记录

url

from django.urls import path, re_path, include
from app01 import views

urlpatterns = [
    re_path(r'^index/$', views.index, name='index')
]

方法1：

view

from django.shortcuts import render, HttpResponse

# Create your views here.

from app01.models import Book   # 导入Book对象

def index(request):
    # 添加表记录

    # 方式1：  # 所有字段必须和modles的一一对应
    book_obj = Book(
        id=1,
        title='pyhon红宝书',
        state=True,
        price=10,
        pub_date='2012-02-21',
        publish='人民出版社'
    )
    book_obj.save()  # 相当于commit提交

    return HttpResponse('<h1>数据操作成功</h1>')

启动django

方法2：

from django.shortcuts import render, HttpResponse

# Create your views here.

from app01.models import Book

def index(request):
    # 添加表记录

    # 方式2： 推荐使用 Book.objects：表的管理器
    book_obj = Book.objects.create(
        title='php',
        state=True,
        price=100,
        pub_date='2018-09-09',
        publish='南京出版社',
    )

    # create返回值就是当前生成表的对象记录
    print(book_obj.title)
    print(book_obj.price)
    print(book_obj.pub_date)

    return HttpResponse('<h1>数据操作成功</h1>')

4、单表操作之查询API

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

<8> count():                返回数据库中匹配查询(QuerySet)的对象数量。

<9> first():                返回第一条记录

<10> last():                返回最后一条记录

<11> exists():              如果QuerySet包含数据，就返回True，否则返回False

<12> 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
<13> 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

<14> distinct():            从返回结果中剔除重复纪录

modles

from django.db import models

# Create your models here.

class Book(models.Model):
    id = models.AutoField(primary_key=True)
    title = models.CharField(max_length=32, unique=True)
    state = models.BooleanField()
    pub_date = models.DateField()
    price = models.DecimalField(max_digits=8, decimal_places=2)   # 999999.00
    publish = models.CharField(max_length=22)                     # 10000000.00  溢出

    def __str__(self):    # 调用Book对象返回title
        return self.title

QuerySet：新的数据类型

<QuerySet [<Book: pyhon红宝书>, <Book: php>]>

　　

  # ######  查询表记录
    """
    1.方法的返回值
    2.方法的调用者
    """

　　（1）all方法

    # 1. all() 调用者：Book.objects   返回值QuerySet对象
    book_list = Book.objects.all()
    print(book_list)        # [obj1, obj2, ....]

    for obj in book_list:
        print(obj.title, obj.price)

    print(book_list[1].title)
    print(book_list[1].price)

　　（2）first last

    # 2. first,last() : 调用者QuerySet对象  返回值：model对象
    book_obj1 = Book.objects.all().first()
    book_obj2 = Book.objects.all()[0]
    print(book_obj1)
    print(book_obj2)

　　（3）filter

   # 3.filter()   调用者：Book.objects  返回值QuerySet对象
    book_list = Book.objects.filter(price=100)  # [obj1,obj2...]
    print(book_list)
    book_list1 = Book.objects.filter(price=100, title='go')
    print(book_list1)

　　（4）get方法

    # 4.get() 有且只有一个返回值，才有意义  返回值model对象
    book_obj1 = Book.objects.get(title='go')

    # book_obj1 = Book.objects.get(title='lalala')  # 没有返回值，报错
    # book_obj2 = Book.objects.get(price=100)     # php go都是price=100  报错
    print(book_obj1)

　　（5）exclude

    # 5.exclude()  返回值QuerySet对象
    book_obj = Book.objects.exclude(title='go')  # 取反
    print(book_obj)

　　

　　（6）order by

    # 6. order by()  调用者QuerySet对象   返回值QuerySet对象
    book_obj1 = Book.objects.order_by('id')
    book_obj2 = Book.objects.order_by('-id')    # 反序
    book_obj3 = Book.objects.order_by('price', 'id')  # price一样的话，按照id排序
    print(book_obj1)
    print(book_obj2)
    print(book_obj3)

　　（7）count

  # 7. count    调用者QuerySet对象  返回值int数字
    ret = Book.objects.all().count()        # 数字
    print(ret)

　　（8） exist

    # 8. exist()
    ret = Book.objects.all()
    ret1 = Book.objects.all().exists()     # limit 1
    if ret:
        print('ok')

    if ret1:
        print('oK2')

　　（9）values

# 9. values()  调用者QuerySet对象  返回者QuerySet对象  

    ret = Book.objects.all()
    for item in ret:
        print(item.title)

    ret1 = Book.objects.all().values('price')
    # < QuerySet[{'price': Decimal('10.00')}, {'price': Decimal('100.00')}, {'price': Decimal('100.00')}] >
    print(ret1)

    ret2 = Book.objects.all().values('price', 'title')
    # <QuerySet [{'price': Decimal('10.00'), 'title': 'pyhon红宝书'}, {'price': Decimal('100.00'), 'title': 'php'}, {'price': Decimal('100.00'), 'title': 'go'}]>
    print(ret2)

    """
    values:

    temp = []

    for obj in Book.objects.all():
        temp.append({
            'price'=obj.price,
            'title'=obj.title,
        })

    return temp
    """

　　（10）values_list

    # 10. values_list方法    调用者QuerySet对象  返回值QuerySet对象
    ret = Book.objects.all().values_list('price', 'title')
    # < QuerySet[(Decimal('10.00'), 'pyhon红宝书'), (Decimal('100.00'), 'php'), (Decimal('100.00'), 'go')] >

    print(ret)

    """
    values:  list字典
        <QuerySet [{'price': Decimal('10.00'), 'title': 'pyhon红宝书'},
                    {'price': Decimal('100.00'), 'title': 'php'},
                    {'price': Decimal('100.00'), 'title': 'go'}]>
    values_list:  元组
        <QuerySet [(Decimal('10.00'), 'pyhon红宝书'),
                    (Decimal('100.00'), 'php'),
                    (Decimal('100.00'), 'go')]>
    """

　　（11）distinct

    # 11. distinct
    ret = Book.objects.all().distinct()   # id不同，不能去重
    print(ret)

    ret1 = Book.objects.all().values('price')
    print(ret1)

    ret = Book.objects.all().values('price').distinct()  # 存在相同price，可以去重
    print(ret)

　　（12）点语法

# 12. 点语法
Book.objects.all().filter('price').order_by('id').filter('title').reverse().first()

5、单表查询之模糊查询

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="python")
Book.objects.filter(title__icontains="python")
Book.objects.filter(title__startswith="py")
Book.objects.filter(pub_date__year=2012)

    # ############   单表查询 模糊查询
    ret = Book.objects.filter(price__gt=100)            # 大于100
    print(ret)
    ret1 = Book.objects.filter(title__startswith='p')   # 以p开头
    print(ret1)
    ret2 = Book.objects.filter(title__startswith='py')
    print(ret2)
    ret3 = Book.objects.filter(title__contains='h')     # 包含h就行
    print(ret3)
    ret4 = Book.objects.filter(title__icontains='h')     # 包含h，H就行
    print(ret4)
    ret5 = Book.objects.filter(price__in=[10, 100])      # 价格是10 或者100
    print(ret5)

    # 对于 pub_date = models.DateField()
    ret6 = Book.objects.filter(pub_date__year=2018)      # year是2018
    print(ret6)
    ret7 = Book.objects.filter(pub_date__month=6)      # year是2018
    print(ret7)

6、单表之删除与修改表记录

　　（1）delete

    # 13. delete
    # 调用者QuerySet对象
    Book.objects.filter(price=200).delete()     # 直接过滤删除
    ret = Book.objects.filter(price=100).delete()
    print(ret)   # (2, {'app01.Book': 2})   返回删除的数据2条

    # 调用者models对象
    Book.objects.filter(price=10).first().delete()    # 先查询再删除

　　（2）update

    # 14. update  调用者QuerySet对象
    ret = Book.objects.filter(title='go').update(title='PYTHON')
    print(ret)