Django—模型—数据查询（字段查询）

• 字段查询

  ---

  def process_query(request):
      # 非过滤器方法
      # get只能返回一条记录
      # 如果记录不存在：DoesNotExist
      # 如果多于一条记录: MultipleObjectsReturned
      # user = User.objects.get(uid__gt=1)
      # print("111")
      # print(user)
  
      # 2 first 返回一个模型对象
      # user = User.objects.first()
      # print(user)
  
      # 3 last最后一条记录
      # user = User.objects.last()
      # print(user)
  
      #4 结果集中的记录数: 必须是QuerySet才能调用count
      # num = User.objects.filter(uid__lt=10).count()
      # print(num)
  
      # 5 判断结果集是否为空
      # flag = User.objects.all().exists()
      # flag = User.objects.filter(uid__lt=5).exists()
      # print(flag)
  
  
      return HttpResponse("query")
  
  # 查询条件的写法
  def process_filter(request):
      # 关系运算
      """
  
      >=     uid__gte=2  uid>=2
      >      uid__gt=2   uid>2
      <      uid__lt=2   uid<2
      <=     uid__lte=2  uid<=2
      ==       uid=2     uid==2  判等
      """
      # filter中多个条件做逻辑与连接
      # data = User.objects.filter(uid__lt=20)
      # uid >=10 and uid < 20
      # data = User.objects.filter(uid__lt=20,uid__gte=10)
      # print(data)
  
      # in 集合运算
      # data = User.objects.filter(uid__in=[9,12,50])
      # print(data)
  
      # is null 判断空
      # data = User.objects.filter(sex__isnull=True)
      # data = User.objects.exclude(sex__isnull=True)
      # print(data)
  
      # 字符串操作
      # startwith 以...开头
      # data = User.objects.filter(username__startswith='张')
      # username__endswith 以..结尾
      # data = User.objects.filter(username__endswith='1')
      # username__contains 包含
      # data = User.objects.filter(username__contains='1')
      # for user in data:
      #     print(user)
  
      # regex正则匹配
      # print(1111)
      # data = User.objects.filter(username__regex=r'3$')
      # for user in data:
      #     print(user)
  
      # 日期查询
      # data = User.objects.filter(regtime__year=2020)
      data = User.objects.filter(regtime="2020-03-11")
      print(data)
  
      return HttpResponse("查询条件的写法")