ORM

创建表(class)

单表

关联表

• 一对一 OneToOne
• 一对多 ForeignKey
• 多对多 ManyToMany

如果存在外键:

1. 一对多:

models.Book.objects.create(title="python", price=12, publish_id=2)
models.Book.objects.create(title="python",price=123, publish_objects)

2. 多对多;

自动创建表
        add() remove()
        --->正向查询
        book=models.Book.objects.filter(id=3)[0]
        author=models.Author.objects.filter(id__gt=2)
        book.author.add(*authors)
        --->反向查询
        author=models.Author.objects.filter(id=2)[0]
        books=models.Book.objects.filter(id__gt=2)
        author.book_set.add(*books)

手动创建表:

class Book2Author(models.Model):
    author=models.ForeignKey("Author")
    book=models.ForeignKey("Book")
    # 创建联合唯一dd
    class Meta:
        unique_together=["author", "book"]

操作表:

    增
        --> create
            models.Book.objects.create(title="python",price=123)
            dic={title="python",price=123}
            models.Book.objects.create(**dic)
        --> save
            obj=Book(title="python", price=12)
            obj.save()
            
            obj=Book()
            book.title="go"
            book.price=123
            obj.save()
            
    删
        models.Book.object.filter(id=2).delete() # 级联删除
        
    改
        Publisher.objects.filter(id=2).update(name="American publisher")
    
    查
        filter all get 三个方法, get返回对象,其他两个返回QuerySet集合
        
        惰性机制: 只用调用时才执行
            设置Django logging:
                ...
                
        __ 双下划线
        models.Tb1.objects.filter(id__gt=3)
        models.Tb1.objects.filter(id__in=[1,2,3])
        models.Tb1.objects.filter(title__contains = "haha")
        models.Tb1.objects.filter(title__icontains = "haha")
        models.Tb1.objects.filter(title__startwith= "P")
        
        models.Publish.objects.filter(book__title="python").values("name")
        
        models.Book.objects.filter(title="python").values("publisher_name")
        
        
        聚合查询
            --> aggregate
                Book.objects.all().aggregate(Avg('price'))
                Book.objects.filter(authors__name='alex').aggregate(Sum('price')
                
        分组查询
            --> annotate
                Book.objects.values("authors__name").annotate(sum('price'))
            
        F查询
            models.Book.objects.all().update(price=F("price")+20)
        
        Q查询:封装条件关键字查询
            models.Book.objects.filter(Q(id=3)|Q(title="Go"))

admin的配置

python manage.py makemigrations
python mange.py migrate
python manage.py createsuperuser        

admin.py
    class Myadmin(admin.ModelAdmin):
        list_display = ("title", "price", "publisher")
        search_fields = ("title", "price")
        list_filter = ("title")
        ordering = ("-id",)
        
    admin.site.registerI(Book, Myadmin);

配置mysql

settings.py

DATABASE{
    'default':{
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'ORM',
        'HOST': '192.168.12.200',
        'PORT': '3306',
        'USER': 'root',
        'password': '123456',
    }
}

__init__.py

import pymysql
pymysql.install_as_MySQLdb()