Student.objects.filter(id=14).delete()

# 1. 先查询到数据模型对象。通过模型对象进行删除
student = Student.objects.filter(pk=13).first()
student.delete()
​
# 2. 直接删除
ret = Student.objects.filter(pk=100).delete()
print(ret)
# 务必写上条件，否则变成了清空表了。ret = Student.objects.filter().delete()

 # stu = Student.objects.create(name="rain", age=33, sex=1, birthday="1996-11-12", clas_id=9, stu_detail_id=7)
​
    # (1) 添加多对多的数据
​
    # 添加多对多方式1
    c1 = Course.objects.get(title="思修")
    c2 = Course.objects.get(title="逻辑学")
    stu.courses.add(c1,c2)
​
    # 添加多对多方式2
    stu = Student.objects.get(name="张三")
    stu.courses.add(5,7)
​
    # 添加多对多方式3
    stu = Student.objects.get(name="李四")
    stu.courses.add(*[6,7])
​
    # (2) 删除多对多记录
​
   stu = Student.objects.get(name="李四")
   stu.courses.remove(7)
​
    # (3) 清空多对多记录：clear方法
​
    stu = Student.objects.get(name="rain")
    stu.courses.clear()
​
    # (4) 重置多对多记录：set方法
​
    stu = Student.objects.get(name="李四")
    stu.courses.set([5,8])
​
    # (5) 多对多记录查询： all
    # 查询李四所报课程的名称
    stu = Student.objects.get(name="李四")
    courses = stu.courses.all()
    courses = stu.courses.all().values("title")
    print(courses)  # <QuerySet [<Course: Course object (5)>, <Course: Course object (8)>]>1.

    # 查询张三的年龄
    ret = Student.objects.filter(name="张三").values("age")
    print(ret) # <QuerySet [{'age': 22}]>
​
    # (1) 查询年龄大于22的学生的姓名以及所在名称班级
    # select db_student.name,db_class.name from db_student inner join db_class on db_student.clas_id = db_class.id where db_student.age>22;
​
    # 方式1 ： Student作为基表
    ret = Student.objects.filter(age__gt=22).values("name","clas__name")
    print(ret)
    # 方式2 ：Clas表作为基表
    ret = Clas.objects.filter(student_list__age__gt=22).values("student_list__name","name")
    print(ret)
​
    # (2) 查询计算机科学与技术2班有哪些学生
​
    ret = Clas.objects.filter(name="计算机科学与技术2班").values("student_list__name")
    print(ret)  #<QuerySet [{'student_list__name': '张三'}, {'student_list__name': '李四'}]>
​
    # (3) 查询张三所报课程的名称
​
    ret = Student.objects.filter(name="张三").values("courses__title")
    print(ret) # <QuerySet [{'courses__title': '近代史'}, {'courses__title': '篮球'}]>
​
    # (4) 查询选修了近代史这门课程学生的姓名和年龄
​
    ret = Course.objects.filter(title="近代史").values("students__name","students__age")
    print(ret) # <QuerySet [{'students__name': '张三', 'students__age': 22}, {'students__name': '李四', 'students__age': 24}]>
​
    # (5) 查询李四的手机号
​
    ret = Student.objects.filter(name='李四').values("stu_detail__tel")
    print(ret)  # <QuerySet [{'stu_detail__tel': '911'}]>
​
​
    # (6) 查询手机号是110的学生的姓名和所在班级名称
​
    # 方式1
    ret = StudentDetail.objects.filter(tel="110").values("stu__name","stu__clas__name")
    print(ret) # <QuerySet [{'stu__name': '张三', 'stu__clas__name': '计算机科学与技术2班'}]>
​
    # 方式2：
    ret = Student.objects.filter(stu_detail__tel="110").values("name","clas__name")
    print(ret) # <QuerySet [{'name': '张三', 'clas__name': '计算机科学与技术2班'}]>

# from django.db.models import Avg, Count, Max, Min
ret = Student.objects.values("sex").annotate(c = Count("name"))
print(ret) # <QuerySet [{'sex': 0, 'c': 1}, {'sex': 1, 'c': 3}]>

>>> Article.objects.all()[:5]   # (LIMIT 5)
>>> Article.objects.all()[5:10]    # (OFFSET 5 LIMIT 5)

articleList=models.Article.objects.all()
​
for article in articleList:
    print(article.title)

queryResult=models.Article.objects.all() # not hits database
print(queryResult) # hits database
for article in queryResult:
    print(article.title)    # hits database

queryset = Book.objects.all()
print(queryset) # hit database
print(queryset) # hit database

queryset = Book.objects.all()
one = queryset[0] # hit database
two = queryset[1] # hit database
print(one)
print(two)

>>> ringo = Person.objects.create(name="Ringo Starr")
>>> paul = Person.objects.create(name="Paul McCartney")
>>> beatles = Group.objects.create(name="The Beatles")
>>> m1 = Membership(person=ringo, group=beatles,
...     date_joined=date(1962, 8, 16),
...     invite_reason="Needed a new drummer.")
>>> m1.save()
>>> beatles.members.all()
[<Person: Ringo Starr>]
>>> ringo.group_set.all()
[<Group: The Beatles>]
>>> m2 = Membership.objects.create(person=paul, group=beatles,
...     date_joined=date(1960, 8, 1),
...     invite_reason="Wanted to form a band.")
>>> beatles.members.all()
[<Person: Ringo Starr>, <Person: Paul McCartney>]

# THIS WILL NOT WORK
>>> beatles.members.add(john)
# NEITHER WILL THIS
>>> beatles.members.create(name="George Harrison")
# AND NEITHER WILL THIS
>>> beatles.members = [john, paul, ringo, george]

>>> # Beatles have broken up
>>> beatles.members.clear()
>>> # Note that this deletes the intermediate model instances
>>> Membership.objects.all()

# Hits the database.
book= models.Book.objects.get(nid=2)
# Hits the database again to get the related Blog object.
print(book.publish.name)

books=models.Book.objects.select_related("publish").all()
for book in books:
     #  Doesn't hit the database, because book.publish
     #  has been prepopulated in the previous query.
     print(book.publish.name)

book=models.Book.objects.select_related("publish").get(nid=1)
print(book.authors.all())

book=models.Book.objects.select_related("publish","").get(nid=1)
print(book.publish)

book=models.Article.objects
　　　　　　　　　　　　　.select_related("publish")
　　　　　　　　　　　　　.select_related("")
　　　　　　　　　　　　　.get(nid=1)  # django 1.7 支持链式操作
print(book.publish)

# 查询所有文章关联的所有标签
books=models.Book.objects.all()
for book in books:
    print(book.authors.all())  #4篇文章: hits database 5

# 查询所有文章关联的所有标签
books=models.Book.objects.prefetch_related("authors").all()
for book in books:
    print(book.authors.all())  #4篇文章: hits database 2

extra(select=None, where=None, params=None, 
      tables=None, order_by=None, select_params=None)

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
​
<p>用户名：<input type="text"><span class="error" style="color: red"></span></p>
​
<script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.js"></script>
<script>
​
    $(":text").blur(function () {
        // 发送Ajax请求
        $.ajax({
            url: "http://127.0.0.1:8008/reg_user/",
            type: "post",
            data: {
                user: $(":text").val(),
            },
            success: function (response) {
                console.log(response);
                $(".error").html(response.msg);
            }
        })
    })
​
</script>
​
</body>
</html>

def test(request):
    import json
    obj=HttpResponse(json.dumps({'name':'yuan'}))
    # obj['Access-Control-Allow-Origin']='*'
    obj['Access-Control-Allow-Origin']='http://127.0.0.1:8004'
    return obj

from django.utils.deprecation import MiddlewareMixin
class MyCorsMiddle(MiddlewareMixin):
    def process_response(self, request, response):
        # 简单请求:
        # 允许http://127.0.0.1:8001域向我发请求
        # ret['Access-Control-Allow-Origin']='http://127.0.0.1:8001'
        # 允许所有人向我发请求
        response['Access-Control-Allow-Origin'] = '*'
        if request.method == 'OPTIONS':
            # 所有的头信息都允许
            response['Access-Control-Allow-Headers'] = '*'
        return response

# (1)
pip install django-cors-headers
​
# (2)
 INSTALLED_APPS = (
 'corsheaders',
)
# (3)
 1 MIDDLEWARE = [
 2     'django.middleware.security.SecurityMiddleware',
 3     'django.contrib.sessions.middleware.SessionMiddleware',
 4     'django.middleware.csrf.CsrfViewMiddleware',
 5     'django.contrib.auth.middleware.AuthenticationMiddleware',
 6     'django.contrib.messages.middleware.MessageMiddleware',
 7     'django.middleware.clickjacking.XFrameOptionsMiddleware',
 8     'corsheaders.middleware.CorsMiddleware',  # 按顺序
 9     'django.middleware.common.CommonMiddleware',  # 按顺序
10 ]
  # 配置白名单
 1 CORS_ALLOW_CREDENTIALS = True#允许携带cookie
 2 CORS_ORIGIN_ALLOW_ALL = True
 3 CORS_ORIGIN_WHITELIST = ( '*')#跨域增加忽略
 4 CORS_ALLOW_METHODS = ( 'DELETE', 'GET', 'OPTIONS', 'PATCH', 'POST', 'PUT', 'VIEW', )
 5 #允许的请求头
 6 CORS_ALLOW_HEADERS = (
 7     'XMLHttpRequest',
 8     'X_FILENAME',
 9     'accept-encoding',
10     'authorization',
11     'content-type',
12     'dnt',
13     'origin',
14     'user-agent',
15     'x-csrftoken',
16     'x-requested-with',
17     'Pragma',
18 )