平均数(Avg)数量(Count),最大(Max),最小(Min),求和(Sum)需要和过滤器调用 aggregate()
查询图书的总阅读量
BookInfo.objects.aggregate(Sum('readcount'))
查询图书的总数:count()
BookInfo.objects.count()
>>> BookInfo.objects.aggregate(Count('readcount'))
{'readcount__count': 4}
sql语句: order by order_by
BookInfo.objects.all() <QuerySet [<BookInfo: 射雕英雄传>, <BookInfo: 天龙八部>, <BookInfo: 笑傲江湖>, <BookInfo: 雪山飞狐>]> >>> BookInfo.objects.all().order_by('readcount') <QuerySet [<BookInfo: 射雕英雄传>, <BookInfo: 笑傲江湖>, <BookInfo: 天龙八部>, <BookInfo: 雪山飞狐>]> >>> BookInfo.objects.all().order_by('-readcount') <QuerySet [<BookInfo: 雪山飞狐>, <BookInfo: 天龙八部>, <BookInfo: 笑傲江湖>, <BookInfo: 射雕英雄传>]>
一对应的模型类对象.多对应的模型类名小写_set
查询图书为1的所有人物的信息
book =BookInfo.objects.get(id=1) >>> book <BookInfo: 射雕英雄传> >>> book.peopleinfo_set.all() <QuerySet [<PeopleInfo: 郭靖>, <PeopleInfo: 黄蓉>, <PeopleInfo: 黄药师>, <PeopleInfo: 欧阳锋>, <PeopleInfo: 梅超风>]>
多对应的模型类对象.多对应的模型类中的关系类属性名(book).pub_date
应用场景:淘宝,京东, 导航栏
person = PeopleInfo.objects.get(id=1) >>> person <PeopleInfo: 郭靖> >>> person.book <BookInfo: 射雕英雄传> >>> person.book_id 1 >>> person.book.name '射雕英雄传' >>> person.book.pub_date datetime.date(1980, 5, 1)
1语法:filter(关联模型类名小写__属性名__条件运算符=值) # 条件运算符 可以没有 一般查询的时候都不会在加上
查询图书,要求图书人物为郭靖
book = BookInfo.objects.filter(peopleinfo__name='郭靖') >>> book <QuerySet [<BookInfo: 射雕英雄传>]>
查询图书 要求图书中人物的描述信息包含八
book = BookInfo.objects.filter(peopleinfo__description__contains='八') >>> book <QuerySet [<BookInfo: 射雕英雄传>, <BookInfo: 天龙八部>]
语法:filter(一模型类关联属性名(外键__模型类属性名__条件运算符=值))
查询书名为‘天龙八部’的所有人物
peole = PeopleInfo.objects.filter(book__name='天龙八部') >>> peole <QuerySet [<PeopleInfo: 乔峰>, <PeopleInfo: 段誉>, <PeopleInfo: 虚竹>, <PeopleInfo: 王语嫣>]>
查询图书阅读量大于30的所有人物
eole = PeopleInfo.objects.filter(book__readcount__gt=30) >>> peole <QuerySet [<PeopleInfo: 乔峰>, <PeopleInfo: 段誉>, <PeopleInfo: 虚竹>, <PeopleInfo: 王语嫣>, <PeopleInfo: 胡 斐>, <PeopleInfo: 苗若兰>, <PeopleInfo: 程灵素>, <PeopleInfo: 袁紫衣>]>
QuerySet :查询集 : Django 的ORM 中存在查询集的概念 也叫查询结果集 从数据库中获取的对象集合
BookInfo.objects.all()[0:2] <QuerySet [<BookInfo: 射雕英雄传>, <BookInfo: 天龙八部>]>
from django.core.paginator import Paginator from django.core.paginator import Paginator >>> books = BookInfo.objects.all() # 查询数据对象 >>> paginator = Paginator(books,2) # 创建分页实例 <string>:1: UnorderedObjectListWarning: Pagination may yield inconsistent results with an unordered object_l ist: <class 'books.models.BookInfo'> QuerySet. >>> pages = paginator.page(1) 获取指定页码的数据 >>> pages <Page 1 of 2> >>> total = paginator.num_pages # 获取分页的数据 >>> total
E:\Python 3.7.9\Django-object\dj11\books\views.py代码如下:
from books.models import PeopleInfo def cx(request): """ 查询数据库操作 get() :param request: :return: """ # 查询id为一的数据 people = PeopleInfo.objects.get(id=1) print(people) # 构造数据类型为字段(json) data = { 'name': people.name, 'gender':people.gender } return JsonResponse(data=data) def cx_all(request): """ 查询数据库 all() :param request: :return: """ # 获取数据 people = PeopleInfo.objects.all().order_by('-gender') print(people) # 定义一个空列表,用来保存 list1= [] # 循环出数据对象 for i in people: data = { 'name': i.name, 'gender': i.gender } # 添加到列表中 list1.append(data) print(list1) return JsonResponse(data=list1,safe=False)
E:\Python 3.7.9\Django-object\dj11\books\urls.py代码如下:
from django.urls import path,re_path from .import views app_name = 'books' urlpatterns = [ # 查询 path('cx/',views.cx), path('cx_all/',views.cx_all,name='cx_all'), ]
运行manager.py,浏览器地址访问:http://127.0.0.1:8000/cx/
E:\Python 3.7.9\Django-object\dj11\books\views.py代码如下:
# 重定向 from django.shortcuts import redirect,reverse from django.http import HttpResponseRedirect def index2(request): """ 重定向 :param request: :return: """ # return HttpResponseRedirect('/cx/') return redirect(reverse('books:cx_all'))
E:\Python 3.7.9\Django-object\dj11\books\urls.py倒数第二行插入路由代码如下:
path('index2/', views.index2),
通过访问:http://127.0.0.1:8000/index2/即可重定向为:http://127.0.0.1:8000/cx_all/