python測試開發django-38.多對多（ManyToManyField）查詢

前言

一個學生能夠對應多個老師，一個老師也能夠教多個學生，這就是一種多對多的關係

models建表

新建一個老師表Teacher，和一個學生表Student

class Teacher(models.Model): '''老師表''' teacher_name = models.CharField(max_length=30, verbose_name="老師", default="") tel = models.CharField(max_length=30, verbose_name="電話", default="") mail = models.CharField(max_length=30, verbose_name="郵箱", default="") class Meta: verbose_name = "老師" verbose_name_plural = verbose_name def __str__(self): return self.teacher_name class Student(models.Model): '''學生表''' student_id = models.CharField(max_length=30, verbose_name="學號", default="") name = models.CharField(max_length=30, verbose_name="姓名", default="") age = models.IntegerField(verbose_name="年齡", default="") # 多對多 teachers = models.ManyToManyField(Teacher, verbose_name="老師") class Meta: verbose_name = "學生" verbose_name_plural = verbose_name def __str__(self): return self.name

以後執行 makemigrations 和migrate，同步數據

python manage.py makemigrations
python manage.py migrate

同步以後數據庫裏面會新增三張表：student、teacher、student_teachers

shell模式新增數據

爲了調試方便，能夠使用django的shell模式，對錶的數據增刪改查操做，打開cmd，cd到manage.py目錄

python manage.py shell

多對多表的增長數據

>>> from hello.models import Teacher, Student >>> t1=Teacher.objects.create(teacher_name='劉老師',tel='155300001111',mail='1000@qq.com') >>> t1.save() >>> t1 <Teacher: Teacher object (1)> >>> t2=Teacher.objects.create(teacher_name='萬老師',tel='155300001112',mail='1001@qq.com') >>> t2.save() >>> t2 <Teacher: Teacher object (2)> >>> s1=Student.objects.create(student_id='11002200',name='張三',age=19) >>> s1.save()  # 方法一：添加id # 能夠添加Teacher對應的id >>> s1.teachers.add(1) # 也能夠添加多個id，逗號隔開 >>> s1.teachers.add(1,2) # 若是添加的是傳一個可迭代對象(list或tupule),能夠用*分開傳入這種方法 >>> s1.teachers.add(*[1,2])  # 方法2、直接添加對象 >>> s1.teachers.add(t1) >>> s1.teachers.add(t2) >>> s1.teachers.add(t1,t2)  # 也能夠先查詢須要添加的對象 >>> ob=Teacher.objects.get(teacher_name='劉老師') >>> ob <Teacher: Teacher object (1)> >>> s2=Student.objects.create(student_id='11002201',name='李四',age=19) >>> s2.teachers.add(ob)

正向查詢

經過student表對象，查詢到對應的teacher

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

反向查詢_set

經過老師名稱，查詢對應關聯的學生，反向查詢的時候在關聯表名稱後面加_set，若是設置related_name參數，就用related_name參數對應名稱查詢
參考上一篇http://www.javashuo.com/article/p-bqquhmpz-bx.html

>>> tea=Teacher.objects.filter(teacher_name='劉老師').first() >>> tea <Teacher: Teacher object (1)> >>> tea.tel '155300001111' # 反向查詢 >>> tea.student_set.all() <QuerySet [<Student: Student object (1)>, <Student: Student object (2)>]> >>> tea.student_set.all()[0].name '張三' >>>

xadmin註冊表

# adminx.py import xadmin from .models import Card, CardDetail, Teacher, Student class ControlTeacher(object): # 顯示的字段 list_display = ["teacher_name", "tel", "mail"] class ControlStudent(object): # 顯示的字段 list_display = ('student_id', 'name', 'age', '老師') # # 定義一個方法，遍歷book的auth，而後用列表返回 def 老師(self, obj): return [x.teacher_name for x in obj.teachers.all()] xadmin.site.register(Teacher, ControlTeacher) xadmin.site.register(Student, ControlStudent)

xadmin後臺顯示效果