一、一对多

• 利用ForeignKey 创建表

注关联表中会自动添加字段后面加_id,相当于publish _id,其中单独的publish包含整个Publish对象

class Book(models.Model):
    name = models.CharField(max_length=20)
    price = models.IntegerField()
    pud_data = models.DateField()
    publish = models.ForeignKey('Publish')


class Publish(models.Model):
    name = models.CharField(max_length=32)
    city = models.CharField(max_length=32)

• 增

• 第一种方法通过真实的字段，也就是在_id添加

def index(request):
    from cm import models
    obj = models.Book.objects.create(
        name = "c#",
        price = 200,
        pud_data = '2008-08-08',
        publish_id= 1
    )
    print(obj)
    return  HttpResponse('ok')

• 第二种通过对象添加，具体的操作是先查找出关联对象，把关联对象直接赋值給属性

• 查

• 正向查找通过对象包含查找

def index(request):
    from cm import models
    obj = models.Book.objects.filter(name="python")
    print(obj[0].publish.city)
    return  HttpResponse('ok')

• 反向查找,通过关联对象查找

• 第一种通过对象反差

def index(request):
    from cm import models
    obj = models.Publish.objects.filter(name="理工")[0]
    obj1 = models.Book.objects.filter(publish=obj).values("name")
    print(obj1)
    return  HttpResponse('ok')

• 第二种通过set反查,通过关联的类后面加_set

def index(request):
    from cm import models
    obj = models.Publish.objects.filter(name="理工")[0]
    obj1 = obj.book_set.all()
    print(obj1)
    return  HttpResponse('ok')

• 第三种直接属性双下滑下接字段，例如publish__name

def index(request):
    from cm import models
    obj = models.Book.objects.filter(publish__name="理工").values("name")
    print(obj)
    return  HttpResponse('ok')

二、多对多

• 利用ManyToManyField创建表

class Book(models.Model):
    name = models.CharField(max_length=20)
    price = models.IntegerField()
    pud_data = models.DateField()
    authors = models.ManyToManyField('Author')

class Author(models.Model):
    name = models.CharField(max_length=32)

• 查

利用查询包含ManyToManyField对象，进行查找关联表

def index(request):
    from cm import models
    obj = models.Book.objects.filter(name="go")
    print(obj[0].authors.all().values('name'))
    return  HttpResponse('ok')

• 增加add,先找到关联对象，在有add添加对象

def index(request):
    from cm import models
    obj = models.Author.objects.all()
    obj1 = models.Book.objects.filter(name="python")
    obj1[0].authors.add(*obj)
    return  HttpResponse('ok')

• 或者直接添加主键

def index(request):
    from cm import models
    obj = [1,2]
    obj1 = models.Book.objects.filter(name="python")
    obj1[0].authors.add(*obj)
    return  HttpResponse('ok')

• remove删除

def index(request):
    from cm import models
    obj = [1,]
    obj1 = models.Book.objects.filter(name="python")
    obj1[0].authors.remove(*obj)
    return  HttpResponse('ok')