django-数据库的增删改查操作——个人学习笔记

django-数据库的增删改查操作

---

models.py中执行如下操作

---

class UserInfo(models.Model):
userid = models.AutoField(primary_key=True)
username = models.CharField(max_length=30, null=False)
password = models.CharField(max_length=128, null=False)
regtime = models.DateTimeField(auto_now=True)

class Meta:
db_table = 'userinfo'
# ordering 排序，默认按照主键排序

def str(self):
return self.username

---

在项目urls.py中执行如下操作

---

urlpatterns = [
path('admin/', admin.site.urls),
path('login/', include('loginapp.urls'))
]

---

在app的urls.py中执行如下操作

---

urlpatterns = [
# path('login/', views.login)
# path('query/', views.query)
# path('curd/', views.curd)
# path('order/', views.order)
# path('dis/', views.distinctview)
# path('fx/', views.fx)
# path('query/', views.process_query, name='curd')
path('group/', views.group)
]

---

views.py试图文件中执行如下操作

1.添加用户记录

def login(request):
增加用户记录 使用save()方法来增加记录
username = UserInfo(username='tom', password='123')
username.save()

2.使用遍历方法创建用户信息

user = {'username': 'wangwang', 'password': '1234'}
UserInfo.objects.create(**user)

3.增加用户方法2

UserInfo.objects.create(username='wangwei', password='111')
批量插入 嵌套create方法在shell中执行
UserInfo.objects.create(UserInfo.objects.create(username='wangjian', password='222'),
UserInfo.objects.create(username='wanghui', password='222'),
UserInfo.objects.create(username='wanglong', password='222'))

4.批量插入方法2

UserInfo.objects.bulk_create([UserInfo(username='huihui', password='222'),
UserInfo(username='dongmao', password='222'),
UserInfo(username='zhouzhou', password='222'),
UserInfo(username='dongmao1', password='222'),
UserInfo(username='zhouzhou1', password='222')
])

6. 修改用户记录 先查看是否有该字段，然后调用字段直接进行修改

user = UserInfo.objects.get(userid=1)
print(user)
user.password = '3333'
user.save()

7. 删除用户记录 使用delete方法删除指定行

user = UserInfo.objects.get(userid=2)
print(user, type(user))
if user:
user.delete()

8.批量删除多条记录

users = UserInfo.objects.filter(userid__gte=2)
print(users)
users.delete()

9.数据查询

firstname = ["张", "李", "郑", "吴", "赵", "周", "王"]
lastname = ["建军", "建辉", "建业", "建党", "建国"]
users = []
for name in range(100):
username = firstname[randint(0, 6)] + lastname[randint(0, 4)]+str(randint(0, 10000))
users.append(UserInfo(username=username, password=str(randint(11111, 999999))))
UserInfo.objects.bulk_create(users)

return HttpResponse("批量查询")

10.使用过滤器查询数据

def query(request):
# all过滤器查询所有数据
users = UserInfo.objects.all()
print(users)
return render(request, 'index.html', locals())

filter 过滤器 条件查询

users = UserInfo.objects.filter(userid__gt=100).filter(userid__lt=200)
print(users)
return render(request, 'index.html', locals())

11.def curd(request):

数据查询

user = UserInfo()
user.username = '王辉'
user.password = '2222222'
user.save()
return HttpResponse("CURD")

12.数据排序 使用order_by()方法进行排序

[:number]切片取第前number条记录
def order(request):
data = UserInfo.objects.order_by('username')
for user in data:
print(user.username)
return HttpResponse("排序")

13.查询指定字段

def curd(request):
data = UserInfo.objects.all().values('username')
for user in data:
print(user)

14.去除查询中重复字段

def distinctview(request):
data = UserInfo.objects.all().values("password").distinct()[:10]
print(data)

15.反序 使用reverse方法

def fx(request):
data = UserInfo.objects.order_by('userid').reverse()
print(data)
return HttpResponse("curd")

16.非过滤器查询方法

def process_query(request):
get方法只能返回一条记录
user = UserInfo.objects.get(userid=100)
print("111")
print(user)

17.使用first方法返回一个对象

user = UserInfo.objects.first()
print(user)

18.返回最后一个对象 使用last()方法

user = UserInfo.objects.last()
print(user)

19.查询结果集中的记录数目

num = UserInfo.objects.filter(userid__gte=17).count()
print(num)

20.判断结果集是否为空

flag = UserInfo.objects.filter(userid__lt=17).all().exists()
print(flag)
return HttpResponse("非过滤器查询方法")

"""
关系运算符的表达式的使用
>= 字段__get=num
> 字段__gt=num
< 字段__lt=num
<= 字段__lte=num
== 字段=num
!= 字段__ne=num
"""

21.多个条件查询的逻辑与连接，查询出大于等于100小于200的用户

user = UserInfo.objects.filter(userid__lt=200, userid__gte=100)
print(user)

22.集合查询

data = UserInfo.objects.filter(userid__in=[17, 18, 19])
print(data)

23.查询字段是否为空

data = UserInfo.objects.filter(username__isnull=True)
print(data)

24.字符串操作查询

__startwith以什么字符串开头的所有字段

data = UserInfo.objects.filter(username__startswith='张')
for user in data:
print(user)

25.使用正则表达式匹配查询 使用————reges方法

data = UserInfo.objects.filter(username__regex=r'3$')
print(data)

26.日期查询操作

data = UserInfo.objects.filter(regtime__year=2021)
print(data)
return HttpResponse("多条件的逻辑与查询")

27.统计查询

def group(request):
#查询最大userid
userid = UserInfo.objects.aggregate(Max('userid'))
print(userid)

查询最小值userid

userid = UserInfo.objects.aggregate(Min('userid'))
print(userid)

统计分组查询

data = UserInfo.objects.values('username').annotate(Count('userid')).filter(userid=30)
print(data)
return HttpResponse("统计查询")