Django下ManytoMany 增删改查
建立学生类老师类多对多关系，用ManytoManyField,迁移同步后自动生成中间表tb_Teacher_Student
# 学生类
class Student(models.Model):
name = models.CharField(max_length=32)
class Meta:
db_table = 'tb_Student'
# 老师类
class Teacher(models.Model):
name = models.CharField(max_length=32)
students = models.ManyToManyField('Student',related_name='teacher')
class Meta:
db_table = 'tb_Teacher'
增,改add()
t1=Teacher(name='jotaro') # 实例化老师
s1=Student(name='dio') # 实例化学生
t1.students.add(s1)
t1.save()
s1.save()
print(t1.name)
# 批量建立对象多对多的关系，存在则覆盖 set()
t1=Teacher(name='jotaro')
s1=Student(name='dio')
s2=Student(name='kira')
s3=Student(name='paul')
s1.save()
s2.save()
s3.save()
t1.save()
t1.students.add(s1)
print(t1.students.all())
t1.students.set([s2,s3])
print(t1.students.all())
1.delete(),当删除其中一方的对象，多对多表里对应的关系行也自动删除
teacher = Teacher.objects.get(students__name='kirakira')
print(teacher.students.all())
stu = Student.objects.get(name='kirakira')
stu.delete()
print(teacher.students.all())
如果单纯想去除单个学生和老师的多对多关系，而不想删除任何一方的数据，可以用remove()
t1=Teacher(name='jotaro')
s1=Student(name='dio')
s1.save()
t1.save()
t1.students.add(s1)
print(t1.students.all())
t1.students.remove(s1)
print(s1)
print(t1.students.all())