Django：数据操作、查询、过滤器、非过滤器方法

# -*- coding: utf-8 -*-
"""
数据操作、查询、过滤器、非过滤器方法
"""



from random import randint

from django.shortcuts import render
from django.http import HttpResponse
from .models import User

# Create your views here.
def handle_data(request):
#增加记录
    # user = User(username='Jack1',password='111222')
    # user.save()

    # 批量创建
    # firstname = "张李赵周王郑"
    # lastname = ["丽莉","德克","好","儿","童费","红英","豆蔻"]
    # users = []
    # for name in range(10):
    #     user = firstname[randint(0,5)] + lastname[randint(0,6)] + str(randint(0,999))
    #     users.append(User(username=user,password=str(randint(111111,999999))))
    # User.objects.bulk_create(users)
    # # User.objects.bulk_create([User(username='test1',password='123456'),User(username='test2')])
    # return HttpResponse("增加数据")

#修改记录
    user = User.objects.get(pk=1)
    user.password = '333'
    user.save()
    return HttpResponse("数据修改")


# 删除记录
#     try:
#         user = User.objects.get(pk=1)  #pk表示主键
#         print(user,type(user))
#         if user:
#             user.delete()
#     except Exception as e:
#         print(e)
#     return HttpResponse("数据删除")


def search_data(request):
    #过滤器1 ： all   查询所有
    # users =  User.objects.all()
    # return render(request, "user_list.html", locals())


    #过滤器2 ：filter
    # filter 相当于SQL中的 Where，可设置条件过滤结果
    # users = User.objects.filter(uid__gt=150).filter(uid__lt=160)   # __gt= : 大于  __lt= :小于
    # return render(request, "user_list.html", locals())

    #过滤器： order_by()   升序排序
    # users = User.objects.filter(uid__gt=150).filter(uid__lt=160).order_by('username')
    # return render(request, "user_list.html", locals())

    #限制结果集
    # users = User.objects.filter(uid__gt=150).filter(uid__lt=160).order_by('username')[:2]   # 显示前两条数据
    # return render(request, "user_list.html", locals())


    #显示指定字段
    # users = User.objects.values('username')
    # return render(request, "user_list.html", locals())


    #去重
    users = User.objects.all().values('username').distinct()[:10]
    return render(request, "user_list.html", locals())


# 非过滤方法
def process_query(request):
    # # 1、get 只能返回一条数据,存在多条满足筛选条件时，报错
    # user = User.objects.get(uid__gt= 173)
    # print(user.username)
    # return HttpResponse(f"get查询结果是：{user.username}")

    # # 2、first 返回一个模型对象
    # user = User.objects.first()
    # print(user.username)
    # return HttpResponse(f"first查询结果是：{user.username}")

    # # 3、last 返回一个模型对象,查询最后一条数据
    # user = User.objects.last()
    # print(user.username)
    # return HttpResponse(f"last查询结果是：{user.username}")

    # # 4、count 显示结果集的数量总数,必须是QuerySet才能调用
    # num = User.objects.filter(uid__gt=100).count()
    # print(num)
    # return HttpResponse(f"count查询结果是：{num}")


    # 5、exists  判断结果集是否为空
    flag = User.objects.filter(uid__gt=100).exists()
    print(flag)
    return HttpResponse(f"exists查询结果是：{flag}")