python测试开发django-38.多对多（ManyToManyField）查询

前言

一个学生能够对应多个老师，一个老师也能够教多个学生，这就是一种多对多的关系

models建表

新建一个老师表Teacher，和一个学生表Student

class Teacher(models.Model): '''老师表''' teacher_name = models.CharField(max_length=30, verbose_name="老师", default="") tel = models.CharField(max_length=30, verbose_name="电话", default="") mail = models.CharField(max_length=30, verbose_name="邮箱", default="") class Meta: verbose_name = "老师" verbose_name_plural = verbose_name def __str__(self): return self.teacher_name class Student(models.Model): '''学生表''' student_id = models.CharField(max_length=30, verbose_name="学号", default="") name = models.CharField(max_length=30, verbose_name="姓名", default="") age = models.IntegerField(verbose_name="年龄", default="") # 多对多 teachers = models.ManyToManyField(Teacher, verbose_name="老师") class Meta: verbose_name = "学生" verbose_name_plural = verbose_name def __str__(self): return self.name

以后执行 makemigrations 和migrate，同步数据

python manage.py makemigrations
python manage.py migrate

同步以后数据库里面会新增三张表：student、teacher、student_teachers

shell模式新增数据

为了调试方便，能够使用django的shell模式，对表的数据增删改查操做，打开cmd，cd到manage.py目录

python manage.py shell

多对多表的增长数据

>>> from hello.models import Teacher, Student >>> t1=Teacher.objects.create(teacher_name='刘老师',tel='155300001111',mail='1000@qq.com') >>> t1.save() >>> t1 <Teacher: Teacher object (1)> >>> t2=Teacher.objects.create(teacher_name='万老师',tel='155300001112',mail='1001@qq.com') >>> t2.save() >>> t2 <Teacher: Teacher object (2)> >>> s1=Student.objects.create(student_id='11002200',name='张三',age=19) >>> s1.save()  # 方法一：添加id # 能够添加Teacher对应的id >>> s1.teachers.add(1) # 也能够添加多个id，逗号隔开 >>> s1.teachers.add(1,2) # 若是添加的是传一个可迭代对象(list或tupule),能够用*分开传入这种方法 >>> s1.teachers.add(*[1,2])  # 方法2、直接添加对象 >>> s1.teachers.add(t1) >>> s1.teachers.add(t2) >>> s1.teachers.add(t1,t2)  # 也能够先查询须要添加的对象 >>> ob=Teacher.objects.get(teacher_name='刘老师') >>> ob <Teacher: Teacher object (1)> >>> s2=Student.objects.create(student_id='11002201',name='李四',age=19) >>> s2.teachers.add(ob)

正向查询

经过student表对象，查询到对应的teacher

>>> from hello.models import Teacher, Student >>> stu=Student.objects.filter(name='李四').first() >>> stu <Student: Student object (2)> >>> stu.student_id '11002201' # 正向查询 >>> stu.teachers.all() <QuerySet [<Teacher: Teacher object (1)>]> >>> stu.teachers.all()[0].teacher_name '刘老师' >>> stu.teachers.all()[0].tel '155300001111'

反向查询_set

经过老师名称，查询对应关联的学生，反向查询的时候在关联表名称后面加_set，若是设置related_name参数，就用related_name参数对应名称查询
参考上一篇http://www.javashuo.com/article/p-bqquhmpz-bx.html

>>> tea=Teacher.objects.filter(teacher_name='刘老师').first() >>> tea <Teacher: Teacher object (1)> >>> tea.tel '155300001111' # 反向查询 >>> tea.student_set.all() <QuerySet [<Student: Student object (1)>, <Student: Student object (2)>]> >>> tea.student_set.all()[0].name '张三' >>>

xadmin注册表

# adminx.py import xadmin from .models import Card, CardDetail, Teacher, Student class ControlTeacher(object): # 显示的字段 list_display = ["teacher_name", "tel", "mail"] class ControlStudent(object): # 显示的字段 list_display = ('student_id', 'name', 'age', '老师') # # 定义一个方法，遍历book的auth，而后用列表返回 def 老师(self, obj): return [x.teacher_name for x in obj.teachers.all()] xadmin.site.register(Teacher, ControlTeacher) xadmin.site.register(Student, ControlStudent)

xadmin后台显示效果