Django—模型—数据查询（Q,F对象+原生sql）

• Q,F对象

  ---

  from django.db.models import Q, F
  from django.http import HttpResponse
  from django.shortcuts import render
  from App.models import User
  
  # Create your views here.
  def process_data(request):
      # 创建一个对象
      # user = User()
      # user.username = '大侠'
      # user.password = '就是不告诉你密码'
      # user.save()
  
      # 修改
      # user = User.objects.get(uid=7)
      #     # print(user)
      #     # user.password = '你猜'
      #     # user.save()
  
      # 删除
      # user = User.objects.get(uid=5)
      # user.delete()
  
      # 查询结果集QuerySet
      #1 all
      # select * from user
      # data = User.objects.all()
  
      # print(data)
      # 获取一条，从结果集中取一条
      # data = data.first()
  
      # filter 过滤结果集
      # data = User.objects.all()
      # # select * from user where uid < 20
      # data = data.filter(uid__lt=20)  # uid < 20
      # data = data.filter(uid__gt=10)
      # print(data)
  
      # 排序
      # 按username升序排列
      # data = User.objects.order_by('username')
      # for user in data:
      #     print(user.username)
  
      # 限制结果集  不能用负的下标
      # 切片 取前两条记录
      # data = User.objects.order_by('username')[:2]
      # 从下标为4记录到下标为9的记录
      # data = User.objects.order_by('uid')[4:10]
      # print(data)
  
      # values 指定字段
      data = User.objects.all().values('username')
      # print(data)
      # for user in data: # user是字典
      #     print(user['username'])
  
      # 去重  distinct
      # data = User.objects.all().values("password").distinct()[:10]
      # data = User.objects.values("password").distinct()[:10]
      # print(data)
  
      # 反序
      # data = User.objects.order_by('uid').reverse()
      # print(data)
  
      return HttpResponse("CURD")
  
  
  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")
  
  
  def handle_group(request):
      from django.db.models import Max,Min,Avg,Sum,Count
      # 统计函数用法
      # select max(uid) from user
      # uid = User.objects.aggregate(Max('uid'))
      # print(uid,type(uid))
  
      # 分组
      # select sex,count(uid) from user group by sex
      # data = User.objects.values('sex').annotate(Count('uid'))
      # select sex,count(uid) from user group by sex having sex=1
      # data = User.objects.values('sex').annotate(Count('uid')).filter(sex=1)
  
      # Q对象：构造逻辑或、逻辑非
      # 查询uid>30或者sex=1
  
      # data = User.objects.filter(Q(uid__gt=30)|Q(sex=1))  # | 逻辑或
  
      # data = User.objects.filter(~Q(uid__gt=30))  # | 逻辑非
      # data = User.objects.filter(~Q(sex=1))  # 不能处理null
  
      # print(data)
      #
      # for user in data:
      #     print(user)
  
      # F对象: 把sex看成User的一个列名
      # data = User.objects.filter(uid=F('sex'))
  
  
      # print(data)
  
  
      return HttpResponse("group")
  
  
  def handle_sql(request):
      # 原生sql
      # 返回一个RawQuerySet
      # data = User.objects.raw("select * from user")
      # print(list(data)) # [obj1,obj2]
  
      # 多表联合查询
      # data = User.objects.raw("select * from user ,detail where user.uid =detail.uid;")
      # print(list(data))
  
  
      # 原始sql查询
      # 可以执行任何sql语句和user无关，
      # 查询结果必须包含主键列
      # data = User.objects.raw("select * from detail")
      username = "oireiot' or '1"
      # sql = "select * from user where username='{}'".format(username)
      # 防止sql注入
      sql = "select * from user where username=%s"
      # sql = "select count(*) from user"
      # print(sql)
      # data = User.objects.raw(sql,[username])
  
      # data = User.objects.raw("select count(*) from user")
  
      # print(list(data))
      # print(data.__dict__)
  
  
      tmp =  input("用户名：")
      # sdkjfksjdf' or '1
      # users = User.objects.raw("select * from user where username='{}'".format(tmp))
  
      # 防止sql注入
      users = User.objects.raw("select * from user where username=%s", ["'sddfsdf' or '1'"])
      print(list(users),type(users))
      return HttpResponse("原生sql")

• 原生sql

  ---

  def index(request):
      #字段查询
      # users = User.objects.filter(username__contains='1',uid__lt=30)
      # users = User.objects.filter(uid__range=[10,20])
  
      # 嵌套查询，data只能返回一个字段
      # data = User.objects.filter(uid__gt=15,uid__lt=20).values('uid')
      # users = User.objects.filter(uid__in = data)
  
      #select count('uid') from user
      # users = User.objects.aggregate(Count('uid'))
      # select sex,count('sex') form user group by sex
      # users = User.objects.values('sex').annotate(Count('sex'))
  
      # 原始sql查询
      # 可以执行任何sql语句和user无关，
      # 查询结果必须包含主键列
      # data = User.objects.raw("select * from detail")
      username = "oireiot' or '1"
      # sql = "select * from user where username='{}'".format(username)
      # 防止sql注入
      sql = "select * from user where username=%s"
      # sql = "select count(*) from user"
      # print(sql)
      # data = User.objects.raw(sql,[username])
  
      # data = User.objects.raw("select count(*) from user")
  
      # print(list(data))
      # print(data.__dict__)
  
      # for value in data:
      #     print(value,type(value))
      # from App.tools import query
  
      # data = query("select * from user")
      #带参数
      # data = query("select * from user where uid=%s",10)
      # print(data)
      return HttpResponse("ok")