django框架基于queryset和双下划线的跨表查询操作详解

  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

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')

#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')

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')

#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')

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')