Python框架篇之Django(Models的多表操作)

一对多

1、添加记录

 #publish_id=2
 Book.objects.create(name="Python进阶",price=77,pub_date="2019-12-12",publish_id=2)
            
#publish=object
Book.objects.create(name="GO",price=23,pub_date="2017-05-12",publish=publish_obj)

2、通过对象查询记录

#正向查询:
book_obj=Book.objects.get(name="python进阶")   
pub_obj=book_obj.publish----》书籍对象对应的出版社对象
pub_obj.name
#反向查询:
pub_obj = Publish.objects.filter(name="人民出版社")[0]
pub_obj.book_set.all().values("name","price")

3、通过filter查询记录(filter values 双下划线__)

 #人民出版社出版过的书籍与价格
ret=Book.objects.filter(publish__name="人民出版社").values("name","price")
                    
#python这本书出版社的名字
ret2=Publish.objects.filter(book__name="python进阶").values("name")
                    
#python这本书出版社的名字
ret3=Book.objects.filter(name="python").values("publish__name")
                    
#北京的出版社出版书的名字
ret4=Book.objects.filter(publish__city="北京").values("name")
                    
#2019年上半年出版过书的出版社的名字
ret5=Book.objects.filter(pub_date__lt="2019-07-01",pub_date__gt="2017-01-01").values("publish__name")
                    

多对多

1、创建多对多的关系 author= models.ManyToManyField(“Author”)(推荐)

2、书籍对象它的所有关联作者 obj=book_obj.authors.all()
绑定多对多的关系 obj.add(*QuerySet)
obj.remove(author_obj)

3、如果想向第三张表插入值的方式绑定关系: 手动创建第三张表

                        # class Book_Author(models.Model):
                        #     book=models.ForeignKey("Book")
                        #     author=models.ForeignKey("Author")                    
                        Book_Author.objects.create(book_id=2,author_id=3)

4、练习


#查询人民出版社出过的所有书籍名字和价格
    #方式一:
pub_obj=Publish.objects.filter(name="人民出版社")[0]
ret=Book.objects.filter(publish=pub_obj).values("name","price")
print(ret)

    #方式二
pub_obj = Publish.objects.filter(name="人民出版社")[0]
print(pub_obj.book_set.all().values("name","price"))
print(type(pub_obj.book_set.all()))

    #方式三:调用publish外键字段
ret=Book.objects.filter(publish__name="人民出版社").values("name","price")
print(ret)

#python这本书出版社的名字
ret2=Publish.objects.filter(book__name="python").values("name")
print(ret2)
ret3=Book.objects.filter(name="python").values("publish__name")
print(ret3)

ret4=Book.objects.filter(publish__city="北京").values("name")
print(ret4)

ret5=Book.objects.filter(pub_date__lt="2017-07-01",pub_date__gt="2017-01-01").values("publish__name")
print(ret5)




    #通过对象的方式绑定关系
book_obj=Book.objects.get(id=3)
print(book_obj.authors.all())
print(type(book_obj.authors.all()))

author_obj=Author.objects.get(id=2)
print(author_obj.book_set.all())


book_obj=Book.objects.get(id=3)
author_objs=Author.objects.all()
book_obj.authors.add(*author_objs)
book_obj.authors.remove(*author_objs)
book_obj.authors.remove(4)



    #创建第三张表
Book_Author.objects.create(book_id=2,author_id=2)

obj=Book.objects.get(id=2)
print(obj.book_author_set.all()[0].author)

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