1.models.py
from django.db import models
#自动生成的关联表的优点是要写的代码比较少，缺点是关联表只能有三列，适用于简单的情况，
#而自定义的关联表可以写很多列，适用于复杂的情况。
class Teachers(models.Model):
name = models.CharField(max_length=32)
#m是连接Classes的通道，在数据库自动创建表app01_teachers_m，
#字段名是id、teachers_id、classes_id
m = models.ManyToManyField('Classes')
class Classes(models.Model):
title = models.CharField(max_length=32)
2. views.py
from django.shortcuts import render,HttpResponse
from app01 import models
def test(request):
# models.Teachers.objects.create(name='小明')
# models.Teachers.objects.create(name='小红')
# models.Teachers.objects.create(name='小方')
#
# models.Classes.objects.create(title='全栈1期')
# models.Classes.objects.create(title='全栈2期')
# models.Classes.objects.create(title='全栈3期')
# models.Classes.objects.create(title='全栈4期')
row = models.Teachers.objects.filter(name='小明').first()
#增
# app01_teachers_m表的classes_id增加1,2,3,4
row.m.add(1,2)
row.m.add(*[3,4])
# 删
# app01_teachers_m表的classes_id删除3,4
row.m.remove(3,4)
# row.m.remove(*[3,4])
#删除全部
row.m.clear()
#改
#app01_teachers_m表的classes_id重设为2,3
row.m.set([2,3])
#查
#找到Classes表中小明老师任教的所有班级
classes_list = row.m.all()
for row in classes_list:
print(row.title)
# 找到Classes表中小明老师任教的全栈2期的行
# row = row.m.filter(title='全栈2期')
#反向操作
#找到任教全栈2期的老师都有谁
row = models.Classes.objects.filter(title='全栈2期').first()
teachers_list = row.teachers_set.all()
for row in teachers_list:
print(row.name)
return HttpResponse('...')
