Django CRM查询（一对多，多对多以及相关的反查）

Posted 2020-11-10 yoyo008

 

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="转介绍",on_delete=models.CASCADE)
    date =  models.DateTimeField(auto_now_add=True)  #auto_now_add自动增加

    def __str__(self):
        return self.name

    class Meta:
        verbose_name_plural = "客户信息表"
        verbose_name = "客户信息表"

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

Enrollment模型：

class Enrollment(models.Model):
    """学员报名信息"""
    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="学期")
    class_type_choices = ((0,‘脱产‘),(1,‘周末‘),(2,‘网络‘))
    start_date = models.DateField()
    end_date = models.DateField()

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使用ForeignKey查询

正向查询

关系模型Enrollment包含模型Customer关联的ForeignKey, 模型Enrollment的实例可以通过关联字段访问Customer实例:

>>> e = Enrollment.objects.get(id=2)  #注意：此处不能用e =Enrollment.objects.filter(id=2)

>>> e.customer                        # 通过关联字段访问Customer实例

修改e.blog并调用save方法存入数据库

>>>e.customer= some_customer

>>> e.save()

如果ForeignKey 字段有null=True 设置（即它允许NULL值），可以分配None来删除对应的关联性

>>> e.customer= None

>>> e.save()

反向查询

已经得到模型Customer的实例，需要查询该以该实例为外键的相关模型（如FollowUpRecord和Enrollment）,可以使用查询集API取出相应的实例。

外键没有指定related_name的相关模型：FollowUpRecord

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

反查找使用 模型类名小写_set.all() ,方法如下：

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

外键指定related_name的相关模型：Enrollment

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

反查找不能使用 模型类名小写_set.all()，需要使用related_name的值，方法如下：

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