Django多對多的增刪改查

Django 多對多 關係

• 多對多，本意就是多個一對多的關係

• 定義多對多 ManyToManyField 字段

  from django.db import models
  
  # 學生類
  class Student(models.Model):
      name = models.CharField(max_length=32)
  
  
  # 老師類
  class Teacher(models.Model):
      name = models.CharField(max_length=32)
      students = models.ManyToManyField(to='Student',related_name='stu')

• 多對多添加

  • 添加一條記錄

  # 老師選擇學生
  teacherobj = models.Teacher.objects.filter(id=1).first()
  studentobj = models.Student.objects.filter(id=1).first()
  teacherobj.students.add(studentobj)
  return Response('ok')

  # 學生選擇老師
  studentobj = models.Student.objects.filter(id=1).first()
  teacherobj = models.Teacher.objects.filter(id=2).first()
  studentobj.stu.add(teacherobj)
  return Response('ok')

  • 添加多條記錄

  # 老師選擇多名學生
  teacherobj = models.Teacher.objects.filter(id=3).first()
  teacherobj.students.add(*[1,2,3,4])
  teacherobj.save()

  # 學生選擇多名老師
  studentobj = models.Student.objects.filter(id=2).first()
  studentobj.stu.add(*[3,4])
  studentobj.save()

  • 添加不重複的記錄

  # 老師選擇多名學生
  teacherobj = models.Teacher.objects.filter(id=3).first()
  teacherobj.students.set(*[1,2,3,4])
  teacherobj.save()

  # 學生選擇多名老師
  studentobj = models.Student.objects.filter(id=2).first()
  studentobj.stu.set(*[3,4])
  studentobj.save()

• 多對多查詢

  # 查詢老師有多少名學生
  teacherobj = models.Teacher.objects.filter(id=3).first()
  stuobj = teacherobj.students.all()

  # 查詢學生有多名老師
  studentobj = models.Student.objects.filter(id=2).first()
  teacherobj = studentobj.stu.all()

• 多對多更新

  # 老師批量換學生
  teacherobj = models.Teacher.objects.filter(id=3).first()
  teacherobj.students.set([1,2,3,4])

  # 學生批量換老師
  studentobj = models.Student.objects.filter(id=3).first()
  studentobj.stu.set([1,2,3,4])

• 多對多刪除

  # 老師刪除一個學生
  teacherobj = models.Teacher.objects.filter(id=3).first()
  studentobj = models.Student.objects.filter(id=2).first()
  teacherobj.students.remove(studentobj)

  # 學生刪除一個老師
  studentobj = models.Student.objects.filter(id=3).first()
  teacherobj = models.Teacher.objects.filter(id=4).first()
  studentobj.stu.remove(teacherobj)
  studentobj.save()

  # 老師刪除全部學生
  teacherobj = models.Teacher.objects.filter(id=1).first()
  teacherobj.students.clear()
  teacherobj.save()

  # 學生刪除全部老師
  studentobj = models.Student.objects.filter(id=3).first()
  studentobj.stu.clear()
  studentobj.save()

• 基於python3.6 Django 2.1.4