day53 url别名反向解析、ORM多表操作、聚合查询、分组查询、F查询、Q查询

1.url别名反向解析

2.ORM多表操作

3.聚合查询

4.分组查询

5.F查询

6.Q查询

url别名反向解析

视图部分

from django.urls import reverse
print(reverse('book_list')) #/book/list/
print(reverse('book_edit',args=(2,))) #/book/edit/1/  url的无名分组参数
print(reverse('book_edit',kwargs={'n': 1,})) #/book/edit/1/ 有名分组参数

return redirect('book_list')
return redirect(reverse('book_list'))

模板部分　　

无参数的
<a class="btn btn-primary" href="{% url 'book_add' %}">添加书籍</a>
# 无名分组参数的
<a href="{% url 'book_edit' books.id 3 4 %}" class="btn btn-warning">编辑</a>
# 有名分组
<a href="{% url 'book_del' books.id %}" class="btn btn-danger">删除</a>
<a href="{% url 'book_del' n=books.id %}" class="btn btn-danger">删除</a>

urls.py的别名写法如下

from django.conf.urls import url
from django.contrib import admin

from app01 import views
from app01 import views
urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^book/list/', views.book_list, name='book_list'),
    url(r'^book/add/', views.book_add,name='book_add'),
    url(r'^book/edit/(d+)/', views.book_edit, name='book_edit'), # /book/edit/2/
    url(r'^book/del/(?P<n>d+)/', views.book_del,name='book_del'), # /book/edit/2/
]

url分发，命名空间

项目主目录下的urls.py

from django.conf.urls import url, include
from django.contrib import admin

from app01 import views

urlpatterns = [
    url(r'^admin/', admin.site.urls),

    # url(r'^index/', views.index,name='index'),
    url(r'^app01/', include('app01.urls',namespace='app01')),
    url(r'^app02/', include('app02.urls',namespace='app02')),
    #/app01/index/
]

app01/urls.py

from app01 import views

urlpatterns = [
    # /index/
    url(r'^index/', views.index, name='index'),
    url(r'^book/list/', views.book_list, name='book_list'),
    url(r'^book/add/', views.book_add, name='book_add'),
    url(r'^book/edit/(d+)/', views.book_edit, name='book_edit'),  # /book/edit/2/
    url(r'^book/del/(?P<n>d+)/', views.book_del, name='book_del'),  # /book/edit/2/
]

app02/urls.py

from app02 import views

urlpatterns = [

    url(r'^index/', views.index, name='index'),

]

app01/views.py

def index(request):
    print(reverse('app01:index'))
    # return HttpResponse('app01的路径:' + reverse('index'))
    return HttpResponse('app01的路径:' + reverse('app01:index'))

app02/views.py

def index(requset):
    print(reverse('app02:index'))
    return HttpResponse('app02的路径: ' + reverse('app02:index'))

　　

ORM多表操作

改

    # 修改
    # 一对一和一对多
    models.Author.objects.filter(name='精华').update(
        name='敬华',
        age=50,
        # ad=models.AuthorDetail.objects.get(id=1),
        ad_id=1,
    )
    # 多对多修改
    obj = models.Book.objects.get(id=2)
    obj.authors.set(['3',]) # 值是字符串,clear + add

查看和执行原生sql

# 查看原生sql 

方式1
        from django.db import connection  #通过这种方式也能查看执行的sql语句
        # print(connection.queries)
	方式2
        settings.py文件中配置如下内容
        LOGGING = {
        'version': 1,
        'disable_existing_loggers': False,
        'handlers': {
            'console':{
                'level':'DEBUG',
                'class':'logging.StreamHandler',
            },
        },
        'loggers': {
            'django.db.backends': {
                'handlers': ['console'],
                'propagate': True,
                'level':'DEBUG',
            },
        }
    }

# 执行原生sql

方式1
        cursor = connection.cursor()
        cursor.execute('select * from app01_book;')
        print(cursor.fetchall())

        方式2
            pymysql
    	方式3
        	ret = models.Author.objects.raw('select * from app01_author;') 
            #只限于本表操作
            print(ret)
            for i in ret:
                print(i.name)

查

基于对象的跨表查询

正向查询和反向查询

A表关联了B表，关联属性在A表，那么通过A表数据查询B表数据时，叫做正向查询

正向查询使用 对象.关联属性名称

反向查询使用 对象.关联模型类名小写

一对一

# 正向查询
# 查看敬华作者的家庭住址
# select app01_authordetail.addr from app01_author inner join app01_authordetail on app01_author.ad_id app01_atuhordetail.id
# where app01_author.name='敬华'
obj = models.Author.objects.get(name='敬华')
print(obj.ad.addr)   #北京
# 查询北京协和的作者名称
# 反向查询
obj = models.AuthorDetail.objects.get(addr='北京协和')
print(obj.author.name)

一对多

查询金鳞岂是池中物这本书的出版社
正向查询
obj = models.Book.objects.get(title='金鳞岂是池中物')
print(obj.publishs.name)

查询马哥出版社出版的书籍有哪些
反向查询
ret = models.Publish.objects.get(name='马哥出版社')
books = ret.book_set.all()  #<QuerySet [<Book: Book object>, <Book: Book object>]>

print(books.values('title'))

多对多

# 查询虹猫蓝兔七侠传是谁写的
# select app01_author.name from app01_book inner join app01_book_authors on app01_book.id =
# app01_book_authors.book_id inner join app01_author on app01_author.id = app01_book_authors.author_id

# 正向查询
# obj = models.Book.objects.get(title='虹猫蓝兔七侠传')
# print(obj.authors.all().values('name'))

# 反向查询
# 查询敬华写了哪些书
# obj = models.Author.objects.get(name='敬华')
# print(obj.book_set.all().values('title'))  

基于双下划线的跨表查询

一对一

查看敬华作者的家庭住址
正向写法
ret =  models.Author.objects.filter(name='敬华').values('ad__addr')
反向写法
ret = models.AuthorDetail.objects.filter(author__name='敬华').values('addr')
print(ret) #<QuerySet [{'addr': '北京'}]>

一对多

查询金鳞岂是池中物这本书的出版社
ret = models.Book.objects.filter(title='金鳞岂是池中物').values('publishs__name')
print(ret) #<QuerySet [{'publishs__name': '小马哥出版社'}]>
ret = models.Publish.objects.filter(book__title='金鳞岂是池中物').values('name')
print(ret) #<QuerySet [{'name': '小马哥出版社'}]>

多对多　

查询虹猫蓝兔七侠传是谁写的
ret = models.Book.objects.filter(title='虹猫蓝兔七侠传').values('authors__name')
print(ret)
ret = models.Author.objects.filter(book__title='虹猫蓝兔七侠传').values('name')
print(ret) #<QuerySet [{'name': '敬华'}, {'name': '杨浩'}]>

　　

聚合查询

from django.db.models import Avg,Max,Min,Count,Sum
# 聚合查询
# ret = models.Book.objects.all().aggregate(Avg('price'))
# ret = models.Book.objects.all().aggregate(a=Avg('price'),m=Max('price'))
# print(ret,type(ret)) #{'price__avg': 15.0} <class 'dict'>
注意结果为字典类型.

　　

分组查询

sql_mode模式

<https://www.cnblogs.com/clschao/articles/9962347.html>

# 统计一下每个出版社出版书的平均价格
# 1.sql查询
select publishs_id,avg(price) from app01_book group by publishs_id;
select avg(app01_book.price) from app01_book inner join app01_publish on 
app01_book.publishs_id = app01_publish.id group by app01_publish.name;

# 2.分组查询
ret = models.Book.objects.values('publishs_id').annotate(a=Avg('price')) # 方式一

ret = models.Publish.objects.annotate(a=Avg('book__price')) # 方式二
# <QuerySet [<Publish: Publish object>, <Publish: Publish object>]>
print(ret.values('a','name'))

　　

F查询

# 查询一下点赞数大于评论数的书籍
'''1.传统方法'''
ret = models.Book.objects.all()
book_list = []
for i in ret:
	if i.dianzan > i.comment:
		book_list.append(i)

'''2.F查询'''
from django.db.models import F
''''针对本表不同字段数据进行对比时或者本表字典做一些统一修改时使用F查询'''
# 点赞数大于评论数的
ret = models.Book.objects.filter(dianzan__gt=F('comment'))

'''F查询也支持统一修改'''
# 所有书籍上调10块
models.Book.objects.all().update(price=F('price')+10) # 支持四则运算

　　

Q查询

from django.db.models import Q
'''
| -- or
& -- and
~ -- not
'''

'''and与和or或'''
ret = models.Book.objects.filter(Q(comment__gt=30)|Q(dianzan__gt=50))

ret = models.Book.objects.filter(Q(comment__gt=30)&Q(dianzan__gt=50))
# 等同于# ret = models.Book.objects.filter(comment__gt=30,dianzan__gt=50)

ret = models.Book.objects.filter(Q(comment__gt=30)|Q(dianzan__gt=50),publishDate__year='2018')
# 注意没有Q包裹的条件,写在Q包裹的条件后面.并且Q查询和publishyear之间是and的关系

'''Q查询多层嵌套'''
ret = models.Book.objects.filter(Q(Q(comment__gt=30)|Q(dianzan__gt=50))&Q(xx=11),publishDate__year='2018')

'''条件取反:波浪线写在Q前面'''
# 取评论数小于等于30 的,或者点赞数大于50的
ret = models.Book.objects.filter(~Q(comment__gt=30)|Q(dianzan__gt=50))