Customer模型：

class Customer(models.Model):

    name = models.CharField(max_length=32)
    qq = models.CharField(max_length=64,unique=True)
    weixin = models.CharField(max_length=64,blank=True,null=True)
    age = models.PositiveSmallIntegerField(blank=True,null=True)
    referral_from = models.ForeignKey("Customer",related_name="my_referrals",
                                      blank=True,null=True,verbose_name="轉介紹",on_delete=models.CASCADE)
    date =  models.DateTimeField(auto_now_add=True)  #auto_now_add自動增加

    def __str__(self):
        return self.name

    class Meta:
        verbose_name_plural = "客戶信息表"
        verbose_name = "客戶信息表"

----------------------------------------------------------
 

Enrollment模型：

class Enrollment(models.Model):
    """學員報名信息"""
    customer = models.ForeignKey("Customer",on_delete=models.CASCADE,related_name=‘entries‘)
    class_grade = models.ForeignKey("ClassList",on_delete=models.CASCADE)
    enrollment_date = models.DateField()
    def __str__(self):
        #return self.customer

    class Meta:
        unique_together =  ("customer","class_grade")
---------------------------------------------------------------------------
 

FollowUpRecord模型

class FollowUpRecord(models.Model):
    customer = models.ForeignKey("Customer",on_delete=models.CASCADE)
    content = models.TextField(max_length=1024)
    def __str__(self):
        return "%s" % self.customer
----------------------------------------------------------------------------
 

ClassList模型：

class ClassList(models.Model):
    semester = models.PositiveSmallIntegerField(verbose_name="學期")
    class_type_choices = ((0,‘脫產‘),(1,‘周末‘),(2,‘網絡‘))
    start_date = models.DateField()
    end_date = models.DateField()

-----------------------------------------------------------------------------------------------------------

使用ForeignKey查詢

正向查詢

關系模型Enrollment包含模型Customer關聯的ForeignKey, 模型Enrollment的實例可以通過關聯字段訪問Customer實例:

>>> e = Enrollment.objects.get(id=2)  #註意：此處不能用e =Enrollment.objects.filter(id=2)

>>> e.customer                        # 通過關聯字段訪問Customer實例

修改e.blog並調用save方法存入數據庫

>>>e.customer= some_customer

>>> e.save()

如果ForeignKey 字段有null=True 設置（即它允許NULL值），可以分配None來刪除對應的關聯性

>>> e.customer= None

>>> e.save()

反向查詢

已經得到模型Customer的實例，需要查詢該以該實例為外鍵的相關模型（如FollowUpRecord和Enrollment）,可以使用查詢集API取出相應的實例。

外鍵沒有指定related_name的相關模型：FollowUpRecord

    customer = models.ForeignKey("Customer",on_delete=models.CASCADE)

反查找使用 模型類名小寫_set.all() ,方法如下：

>>>c = Customer.objects.get(id=1)
>>>c.followuprecord_set.all()

外鍵指定related_name的相關模型：Enrollment

customer = models.ForeignKey("Customer",on_delete=models.CASCADE,related_name=‘entries‘)

反查找不能使用 模型類名小寫_set.all()，需要使用related_name的值，方法如下：

>>>c = Customer.objects.get(id=1)
>>>c.entries.all()

Django CRM查詢（一對多，多對多以及相關的反查）