• • • 準備表
    • 一對一操作
    • 一對多操作
    • 多對多操作
    • 常用方法

準備表

建立如下幾張表

from django.shortcuts import HttpResponse, render, redirect
from django.db import models


class Class(models.Model):
    id = models.AutoField(primary_key=True)
    cname = models.CharField(max_length=32)
    cdata = models.DateField()

    def
 
 __str__(self):
        return "%s" % [self.__class__, self.cname]


class Student(models.Model):
    id = models.AutoField(primary_key=True)
    sname = models.CharField(max_length=32)

    # 一對多
    # cid = models.ForeignKey(to="Class",to_field="id",related_name="student")
    cid = models.ForeignKey(to="Class"
 
, to_field="id")

    # 一對一
    detail = models.OneToOneField("StudentDetail", to_field="id")
    # 等同於如下的程式碼
    # detail = models.ForeignKey(to="StudentDetail",to_field="id",unique=True)

    def __str__(self):
        return "%s" % [self.sname]


# #建立多對多  第一種方法
# class Teacher(models.Model):
#     id = models.AutoField(primary_key=True)
 

#     tname = models.CharField(max_length=32)
#
#
# class Teacher2Class(models.Model):m
#     id = models.AutoField(primary_key=True)
#     tid = models.ForeignKey(to="Teacher",to_field="id")
#     cid = models.ForeignKey(to="Class",to_field="id")
#
#     class Meta:
#         unique_together = ("tid","cid")


# 建立多對多  第二種方法
class Teacher(models.Model):
    id = models.AutoField(primary_key=True)
    tname = models.CharField(max_length=32)
    cid = models.ManyToManyField(to="Class",name="teacher")


# 建立多對多  第3種方法
# class Teacher(models.Model):
#     id = models.AutoField(primary_key=True)
#     tname = models.CharField(max_length=32)
#     cid_tid = models.ManyToManyField(to="Class",
#                                      through="Teacher2Class",
#                                      through_fields=("tid", "cid"))
#
# class Teacher2Class(models.Model):
#     id = models.AutoField(primary_key=True)
#     tid = models.ForeignKey(to="Teacher", to_field="id")
#     cid = models.ForeignKey(to="Class", to_field="id")
#
#     class Meta:
#         unique_together = ("tid", "cid")


class StudentDetail(models.Model):
    id = models.AutoField(primary_key=True)
    height = models.PositiveIntegerField()
    email = models.EmailField()
    memo = models.CharField(max_length=128)

需要注意的如下：

  # 一對多
    # cid = models.ForeignKey(to="Class",to_field="id",related_name="student")
    cid = models.ForeignKey(to="Class", to_field="id")

    # 一對一
    detail = models.OneToOneField("StudentDetail", to_field="id")
    # 等同於如下的程式碼
    # detail = models.ForeignKey(to="StudentDetail",to_field="id",unique=True)

來看下幾個表的表名、欄位名
app01_class班級表：

app01_student學生表：

app01_studentdetail學生資訊表：

app01_class老師表：

app01_teacher2class班級老師表：

以上的app01_teacher2class表是通過第3種方法建立的，我們來看下第一種、第二方法建立的表名、欄位名是怎樣的？

通過方法1 建立班級-老師對應表如下：

通過方法2 建立班級-老師對應表如下：

一對一操作

正向查詢（由學生資訊表查詢學生詳情表）

stu = models.Student.objects.first()
stu.detail.email
'[email protected]'

反向查詢（由學生詳情表反向查詢學生資訊表）

detail = models.StudentDetail.objects.get(id=1)
detail.student.sname
'小一

一對多操作

正向查詢（由學生表查詢班級表）

from app01 import models
stu = models.Student.objects.first()
stu.cid_id
1
stu.cid.cname
'全棧1期'

反向查詢（由班級表查詢學生表）

cls = models.Class.objects.first()
cls.student_set.all()
<QuerySet [<Student: ['小一']>, <Student: ['小二']>]>

注意：

如果不在外來鍵的欄位中設定related_name的話，預設就用表名_set。
如果設定了related_name=”students”，反向查詢時可直接使用students進行反向查詢。

cls.students.all() 

多對多操作

正向查詢（由老師表查詢班級表）

from app01 import models
tea = models.Teacher.objects.first()
tea.cid_tid
<django.db.models.fields.related_descriptors.create_forward_many_to_many_manager.<locals>.ManyRelatedManager object at 0x05C110F0>

tea.cid_tid.all()
<QuerySet [<Class: [<class 'app01.models.Class'>, '全棧1期']>, <Class: [<class 'app01.models.Class'>, '全棧2期']>]>

first = tea.cid_tid.first()
first
<Class: [<class 'app01.models.Class'>, '全棧1期']>

first.cname
'全棧1期'

first.student_set
<django.db.models.fields.related_descriptors.create_reverse_many_to_one_manager.<locals>.RelatedManager object at 0x03283870>

first.student_set.all()
<QuerySet [<Student: ['小一']>, <Student: ['小二']>]>

反向查詢（由班級表反向查詢老師表）

cls = models.Class.objects.first()
cls.student_set
<django.db.models.fields.related_descriptors.create_reverse_many_to_one_manager.<locals>.RelatedManager object at 0x03283070>

cls.teacher_set
<django.db.models.fields.related_descriptors.create_forward_many_to_many_manager.<locals>.ManyRelatedManager object at 0x03224710>

cls.teacher_set.all()
<QuerySet [<Teacher: Teacher object>, <Teacher: Teacher object>]>

cls.teacher_set.all().first()
<Teacher: Teacher object>

cls.teacher_set.all().first().cid_tid
<django.db.models.fields.related_descriptors.create_forward_many_to_many_manager.<locals>.ManyRelatedManager object at 0x032A2790>

cls.teacher_set.all().first().tname
'王老師'

常用方法

create()

from app01 import models
import datetime
teacher = models.Teacher.objects.get(id=1)
teacher.cid.create(cname="linux2",cdata=datetime.datetime.now())
<Class: [<class 'app01.models.Class'>, 'linux2']>

多對對

cls = models.Class.objects.get(id=1)
cls.teacher_set.create(tname="egon")
<Teacher: Teacher object>

import datetime
cls = models.Class.objects.first()
cls.student_set.create(sname="王七",detail_id=4)

stu = models.Student.objects.create(sname="wyf",detail_id=5,cid_id=2)

以下方式對多對多不行！！

add()

from app01 import models
import datetime
cls = models.Class.objects.all()
models.Teacher.objects.first().cid.add(*cls)

set\remove\clear

tea = models.Teacher.objects.first()
tea.cid.set([4,3])
tea.cid.remove(3)
tea.cid.clear()

了不起的雙下劃線

models.Class.objects.filter(student__sname__contains="d")
<QuerySet [<Class: [<class 'app01.models.Class'>, 'python']>, <Class: [<class 'app01.models.Class'>, 'sfsdf']>]>

models.Class.objects.values("cname")
<QuerySet [{'cname': 'linux'}, {'cname': 'python'}, {'cname': 'sfsdf'}]>

models.Class.objects.values("cname","student__sname")
<QuerySet [{'cname': 'linux', 'student__sname': 'wyf'}, {'cname': 'python', 'student__sname': 'wfdsd'}, {'cname': 'sfsdf', 'student__sname': 'fdgerter'}]>

以下方法不可行！！

models.Class.objects.first().values("cname","student__sname")
Traceback (most recent call last):
  File "<input>", line 1, in <module>
AttributeError: 'Class' object has no attribute 'values'

models.Class.objects.all().values("cname","student__detail__email")

<QuerySet [{'cname': 'linux', 'student__detail__email': '[email protected]'}, {'cname': 'python', 'student__detail__email': '[email protected]'}, {'cname': 'sfsdf', 'student__detail__email': '[email protected]'}, {'cname': 'linux', 'student__detail__email': '[email protected]'}]>