1.Django 3.1.3新建project时会报错。
C:\Users\season\workspace2>django-admin.py startproject tango_with_django_project
报错信息如下：
ImportError(
'django-admin.py was deprecated in Django 3.1 and removed in Django '
'4.0. Please manually remove this script from your virtual environment '
'and use django-admin instead.'
认真阅读报错信息，就会发现解决措施“use django-admin instead of django-admin.py”。
C:\Users\season\workspace2>django-admin startproject tango_with_django_project
2.多对多关系
多对多关系建立：最好使用默认id作为主键，不要取primary_key=True，否则多对多关系可能无法建立。
https://docs.djangoproject.com/zh-hans/3.1/topics/db/models/
Django 允许你指定用于控制多对多关系的模型。你可以在中间模型当中添加额外的字段。在实例化 ManyToManyField 的时候使用 through 参数指定多对多关系使用哪个中间模型。**最好使用默认id作为主键，不要取primary_key=True，否则多对多关系可能无法建立。**例子代码如下：
from django.db import models
class Employee(models.Model):
eid = models.CharField(max_length=200,default='1')
name = models.CharField(max_length=200,null=True)
dept_code = models.CharField(max_length=200,null=True)
GENDER_CHOICES = (
(u'Male', u'Male'),
(u'Female', u'Female'),
)
gender = models.CharField(max_length=200,choices=GENDER_CHOICES,null=True)
on_board = models.BooleanField(null=True)
Range_CHOICES = (
(u'R1', u'R1'),
(u'R2', u'R2'),
(u'R3', u'R3'),
(u'R4', u'R4'),
)
Range = models.CharField(max_length=200,choices=Range_CHOICES,null=True)
def __str__(self):
return self.name
class Teacher(models.Model):
tid = models.CharField(max_length=200,default='1')
name = models.CharField(max_length=200,null=True)
dept = models.CharField(max_length=200,null=True)
GENDER_CHOICES = (
(u'Male', u'Male'),
(u'Female', u'Female'),
)
gender = models.CharField(max_length=200,choices=GENDER_CHOICES,null=True)
on_board = models.BooleanField(null=True)
GRADE_CHOICES = (
(u'Junior', u'Junior'),
(u'Middle', u'Middle'),
(u'Senior', u'Senior'),
)
teacher_grade = models.CharField(max_length=200,choices=GRADE_CHOICES,null=True)
def __str__(self):
return self.name
class Subject(models.Model):
Subject_id = models.CharField(max_length=200,default='1')
subject_name = models.CharField(max_length=200)
teacher = models.ForeignKey(Teacher, on_delete=models.CASCADE,null=True)
employee = models.ManyToManyField(Employee, through='Employee_Subject')
def __str__(self):
return '%s.%s' % (self.Subject_id, self.subject_name)
class Employee_Subject(models.Model):
subject = models.ForeignKey(Subject,on_delete=models.CASCADE)
employee = models.ForeignKey(Employee,on_delete=models.CASCADE)
def __str__(self):
return '%s : %s' % (self.subject.subject_name, self.employee.name)
3.一对多的“反向” 关联
https://blog.csdn.net/jingxiao95/article/details/89035588
解释
反向查询：一查找多,是反向查找。
无外键类的具体对象.有外键的小写类名_set。
无外键类是一,有外键是多。
一的具体对象.多的类名小写_set 查到一的具体对象下的所有多的对象
eg:
一个出版社对应多本书，以出版社为标准查找书，反向查找。
一个出版社对象.书类_set 查到出版社下的书籍对象,这个书籍对象默认是一个QuerySet对象。
查到一个出版社具体对象下的所有的书。
清晰的例子：
model.py
#出版社类(表)
class Publisher(models.Model):
pid = models.AutoField(primary_key=True)
pname = models.CharField(max_length=32)
#书籍类(表)
class Books(models.Model):
bid = models.AutoField(primary_key=True)
bname = models.CharField(max_length=32)
publisher_obj = models.ForeignKey('Publisher')
- 展示出版社的方法一:
- views.py内:
def show_publisher(request):
# 获取出版社对象列表
publisher_obj_list = models.Publisher.objects.all()
# 获取书籍,通过书籍中的外键对象publisher_obj
# 循环这个出版社对象列表,在书籍表中匹配每一个出版社对象,匹配到就返回书籍对象列表，没有就是空的对象列表,该书籍对象,有具体的出版社对象
books_obj_list = []
for publishers_obj in publisher_obj_list:
#获取到books_obj可能是一个列表
books_obj = models.Books.objects.filter(publisher_obj=publishers_obj)
#将books_obj列表里面的每一个内容拿出来,加到列表内
books_obj_list.extend(books_obj)
return render(request, 'show_publisher.html',
{
"publisher_obj_list": publisher_obj_list, "books_obj_list": books_obj_list})
template内
<table border="1">
<thead>
<tr>
<th>序号</th>
<th>出版社名字</th>
<th>书籍</th>
</tr>
</thead>
<tbody>
{
% for publisher_obj in publisher_obj_list %}
<tr>
#序号
<td>{
{
forloop.counter }}</td>
{
# 出版社名字 #}
<td>{
{
publisher_obj.pname }}</td>
{
# 书籍名字#}
<td>
循环书籍对象列表(每一个书籍都有一个对应的publisher_obj)
{
% for books_obj in books_obj_list %}
判断如果这个出版社对象与书籍的出版社对象相同,获取该书籍的名字
{
% if publisher_obj == books_obj.publisher_obj %}
《{
{
books_obj.bname }}》
{
% endif %}
{
% endfor %}
{
% endfor %}
</td>
- 展示出版社的方法二:
- views.py
def show_publisher(request):
# 获取出版社对象列表
publisher_obj_list = models.Publisher.objects.all()
return render(request, 'show_publisher.html',
{
"publisher_obj_list": publisher_obj_list,})
template内
#反向查找:通过一查找多
#无外键的具体对象(一的具体对象).有外键的小写类名(多的类名小写)_set.all()
#反向查找默认返回的是一个QuerySet对象#}
<td>
{
% for book_obj in publisher_obj.books_set.all %}
《{
{
book_obj.bname }}》
{
% endfor %}
</td>
4.admin界面无法删除数据库数据时，方法一：可以用SQLite Studio来强行删除。方法二：调整modoel中的__str__方法。
class Employee_Subject(models.Model):
subject = models.ForeignKey(Subject,on_delete=models.CASCADE)
employee = models.ForeignKey(Employee,on_delete=models.CASCADE)
#def __str__(self):
#return '%s : %s' % (self.subject.subject_name, self.employee.name)
5.我的例子
-
界面
-
models.py
from django.db import models
class Employee(models.Model):
eid = models.CharField(max_length=200,default='1')
name = models.CharField(max_length=200,null=True)
dept_code = models.CharField(max_length=200,null=True)
GENDER_CHOICES = (
(u'Male', u'Male'),
(u'Female', u'Female'),
)
gender = models.CharField(max_length=200,choices=GENDER_CHOICES,null=True)
on_board = models.BooleanField(null=True)
Range_CHOICES = (
(u'R1', u'R1'),
(u'R2', u'R2'),
(u'R3', u'R3'),
(u'R4', u'R4'),
)
Range = models.CharField(max_length=200,choices=Range_CHOICES,null=True)
def __str__(self):
return self.name
class Teacher(models.Model):
tid = models.CharField(max_length=200,default='1')
name = models.CharField(max_length=200,null=True)
dept = models.CharField(max_length=200,null=True)
GENDER_CHOICES = (
(u'Male', u'Male'),
(u'Female', u'Female'),
)
gender = models.CharField(max_length=200,choices=GENDER_CHOICES,null=True)
on_board = models.BooleanField(null=True)
GRADE_CHOICES = (
(u'Junior', u'Junior'),
(u'Middle', u'Middle'),
(u'Senior', u'Senior'),
)
teacher_grade = models.CharField(max_length=200,choices=GRADE_CHOICES,null=True)
def __str__(self):
return self.name
class Subject(models.Model):
Subject_id = models.CharField(max_length=200,default='1')
subject_name = models.CharField(max_length=200)
teacher = models.ForeignKey(Teacher, on_delete=models.CASCADE,null=True)
employee = models.ManyToManyField(Employee, through='Employee_Subject')
def __str__(self):
return '%s.%s' % (self.Subject_id, self.subject_name)
class Employee_Subject(models.Model):
subject = models.ForeignKey(Subject,on_delete=models.CASCADE)
employee = models.ForeignKey(Employee,on_delete=models.CASCADE)
def __str__(self):
return '%s : %s' % (self.subject.subject_name, self.employee.name)
- views.py
from django.shortcuts import render
from .models import Subject,Employee,Employee_Subject,Teacher
#from .models import Subject,Employee,Teacher
# Create your views here.
def index(request):
Subject_list = Subject.objects.order_by('-Subject_id').all()
Employee_Subject_list = Employee_Subject.objects.all()
Teacher_list = Teacher.objects.all()
subject_obj_list = []
for Teacher_obj in Teacher_list:
subject_obj = Subject.objects.filter(teacher = Teacher_obj)
subject_obj_list.extend(subject_obj)
context = {
'Subject_list':Subject_list,
'Employee_Subject_list':Employee_Subject_list,
'Teacher_list':Teacher_list,
'subject_obj_list':subject_obj_list,
}
return render(request,'myclass/index.html',context=context)
- index.html
<html>
<head>
<title>notice</title>
</head>
<body>
<table>
<p>课程信息</p>
<tr align="center" style="color:White;background-color:#3366FF;font-family:微軟正黑體,Tahoma,Arial,微軟雅黑體;font-size:14px;">
<th scope="col">Subject_id</th>
<th scope="col">subject_name</th>
<th scope="col">teacher.name</th>
</tr>
{
% for item in Subject_list %}
<tr align="center" valign="middle" style="color:Black;background-color:#EFF3FB;border-color:#E0E0E0;border-width:1px;border-style:solid;height:26px;">
<td>{
{
item.Subject_id }}</td>
<td>{
{
item.subject_name }}</td>
<td>{
{
item.teacher.name }}</td>
</tr>
{
% endfor %}
</table>
<table>
<p>学员选课信息</p>
<tr align="center" style="color:White;background-color:#3366FF;font-family:微軟正黑體,Tahoma,Arial,微軟雅黑體;font-size:14px;">
<th scope="col">employee.name</th>
<th scope="col">Subject_id</th>
<th scope="col">subject_name</th>
<th scope="col">teacher</th>
</tr>
{
% for item in Employee_Subject_list %}
<tr align="center" valign="middle" style="color:Black;background-color:#EFF3FB;border-color:#E0E0E0;border-width:1px;border-style:solid;height:26px;">
<td>{
{
item.employee.name }}</td>
<td>{
{
item.subject.Subject_id }}</td>
<td>{
{
item.subject.subject_name }}</td>
<td>{
{
item.subject.teacher.name }}</td>
</tr>
{
% endfor %}
</table>
<table>
<p>讲师信息</p>
<tr align="center" style="color:White;background-color:#3366FF;font-family:微軟正黑體,Tahoma,Arial,微軟雅黑體;font-size:14px;">
<th scope="col">tid</th>
<th scope="col">name</th>
<th scope="col">dept</th>
<th scope="col">gender</th>
<th scope="col">on_board</th>
<th scope="col">teacher_grade</th>
<th scope="col">subject_name</th>
</tr>
{
% for item in Teacher_list %}
<tr align="center" valign="middle" style="color:Black;background-color:#EFF3FB;border-color:#E0E0E0;border-width:1px;border-style:solid;height:26px;">
<td>{
{
item.tid }}</td>
<td>{
{
item.name }}</td>
<td>{
{
item.dept }}</td>
<td>{
{
item.gender }}</td>
<td>{
{
item.on_board }}</td>
<td>{
{
item.teacher_grade }}</td>
<td>
{
% for subject_obj in subject_obj_list %}
{
% if item == subject_obj.teacher %}
{
{
subject_obj.subject_name }}
{
% endif %}
{
% endfor %}
</td>
</tr>
{
% endfor %}
</table>
<table>
<p>讲师信息2</p>
<tr align="center" style="color:White;background-color:#3366FF;font-family:微軟正黑體,Tahoma,Arial,微軟雅黑體;font-size:14px;">
<th scope="col">tid</th>
<th scope="col">name</th>
<th scope="col">dept</th>
<th scope="col">gender</th>
<th scope="col">on_board</th>
<th scope="col">teacher_grade</th>
<th scope="col">subject_name</th>
</tr>
{
% for item in Teacher_list %}
<tr align="center" valign="middle" style="color:Black;background-color:#EFF3FB;border-color:#E0E0E0;border-width:1px;border-style:solid;height:26px;">
<td>{
{
item.tid }}</td>
<td>{
{
item.name }}</td>
<td>{
{
item.dept }}</td>
<td>{
{
item.gender }}</td>
<td>{
{
item.on_board }}</td>
<td>{
{
item.teacher_grade }}</td>
<td>
{
% for subject_item in item.subject_set.all %}
{
{
subject_item.subject_name }}
{
% endfor %}
</td>
</tr>
{
% endfor %}
</table>
</body>