django之基于queryset和双下划线的跨表查询

前面篇随笔写的是基于对象的跨表查询：对象.objects.filter(。。。) 对象.关联对象_set.all(...) -->反向

基于对象的跨表查询例如：

    book_obj= Book.objects.filter(id=4).first() #注意多了个first

    print(book_obj) #go 这里得到的是一个models对象

    print(book_obj.publish.name) #桔子出版社

这篇随笔主要写的是基于双下划线的跨表查询，其本质是使用join连接其他表进行查询

一对多

def query(request):

    #正向查询

    ret1=Book.objects.filter(title='西游记').values("publish__name")

    print(ret1)  #<QuerySet [{'publish__name': '榴莲出版社'}]>

    print(ret1.first(),type(ret1.first())) #{'publish__name': '榴莲出版社'} <class 'dict'> 注意key 为 publish__name

    print(ret1.first()['publish__name']) # 榴莲出版社

    #反向查询

    ret2=Publish.objects.filter(book__title="西游记").values('name') #这里的book是表名称，book表里面有字段 title

    print('---------------------------------')

    print(ret2)  #<QuerySet [{'name': '榴莲出版社'}]>

    print(ret2.first()['name'])#榴莲出版社

　　return HttpResponse('ok')

多对多

#查询python书的作者的名字和年龄
def query(request):

    #正向查询

    ret = Book.objects.filter(title="python").values("authors__name","authors__age")

    print(ret) #注意结果的key

    #结果 <QuerySet [{'authors__name': 'wang', 'authors__age': 27}, {'authors__name': 'xiao', 'authors__age': 25}, {'authors__name': 'zhang', 'authors__age': 26}]>

    #反向查询

    ret = Author.objects.filter(book__title="python").values("name","age")

    print(ret) #区分正向查询的key

    #结果 <QuerySet [{'name': 'wang', 'age': 27}, {'name': 'xiao', 'age': 25}, {'name': 'zhang', 'age': 26}]>

    return HttpResponse('ok')

一对一

例子：查询名字为 xiao 的gf是什么
def query(request):

    #正向查询

    ret=Author.objects.filter(name='xiao').values('ad__gf') #Author设置了外键到 AuthorDetail

    print(ret) #<QuerySet [{'ad__gf': '刘诗诗'}]>

    #反向查询

    ret=AuthorDetail.objects.filter(author__name='xiao').values('gf')

    print(ret) #<QuerySet [{'gf': '刘诗诗'}]>

    return HttpResponse('ok')

下面进行跨多表查询，涉及三个表或者以上

#查询西瓜出版社出版过的书籍和书籍作者的名字
def query(request):

    #正向

    ret=Book.objects.filter(publish__name="西瓜出版社").values_list("title",'authors__name')

    print(ret)

#<QuerySet [('三国演义', 'zhang'), ('python', 'xiao'), ('python', 'zhang'), ('python', 'wang')]>

   #反向

    ret = Publish.objects.filter(name="西瓜出版社").values_list("book__title","book__authors__age","book__authors__name")

    print(ret)

#<QuerySet [('三国演义', 26, 'zhang'), ('python', 25, 'xiao'), ('python', 26, 'zhang'), ('python', 27, 'wang')]>

    return HttpResponse('ok')

手机号以11开头的作者出版过的所有书籍名称以及出版社名称

def query(request):
    #正向
    ret = Book.objects.filter(authors__ad__tel__startswith="11").values("title","publish__name")
    print(ret)
    #< QuerySet[{'title': 'python', 'publish__name': '西瓜出版社'}, {'title': '三国演义', 'publish__name': '西瓜出版社'}] >
    #反向
    ret = Author.objects.filter(ad__tel__startswith="11").values("book__title","book__publish__name")
    print(ret)
#<QuerySet [{'book__title': '三国演义', 'book__publish__name': '西瓜出版社'}, {'book__title': 'python', 'book__publish__name': '西瓜出版社'}]>
    return HttpResponse('查询成功')