Django ORM JOIN 查询答案

【问题标题】：Django ORM JOIN queryDjango ORM JOIN 查询
【发布时间】：2014-06-13 13:14:38
【问题描述】：

我有 2 个模型

class ShipmentBagSealMapping(models.Model):
    bag_seal = models.CharField(max_length = 255)
    status = models.CharField(max_length = 255, default = 'open')
    time = models.DateTimeField( auto_now_add = True, db_index = True)
    shipment_id = models.ForeignKey('Shipment', related_name = 'bags')



class Shipment(models.Model):
    job_id = models.CharField(max_length = 255)
    time = models.DateTimeField( auto_now_add = True, db_index = True)

我想编写一个 JOIN 查询，它告诉我ShipmentBagSealMapping 和status = close 中的记录数以及Shipment 的时间在[start_time and end_time] 范围内。

这是我尝试过的：

total_bags = ShipmentBagSealMapping.objects.filter(shipments__time__range = [start_time,end_time],status='close').values('bag_seal').distinct().count()

但它会抛出一个错误说：-

Cannot resolve keyword 'shipments' into field. Choices are: bag_seal, id, shipment_id, status, time

我该怎么做？

【问题讨论】：

标签： django django-models django-orm

【解决方案1】：

应该这样做：

total_bags = ShipmentBagSealMapping.objects.filter(shipment_id__time__range = [start_time,end_time],status='close').values('bag_seal').distinct().count()

看到您已将该字段定义为shipment_id 而不是shipments

【讨论】：

哦，是的...非常感谢。 :)
你能不能也看看这个问题。 stackoverflow.com/questions/23306953/…谢谢

【解决方案2】：

Django 会自动在你的 ForeignKey 中添加 _id，所以做一些这样的改变可能会有所帮助

class ShipmentBagSealMapping(model.Model):
bag_seal = models.CharField(max_length = 255)
status = models.CharField(max_length = 255 )
time = models.DateTimeField( auto_now_add = True)
shipments = models.ForeignKey('Shipment', related_name = 'bags')

【讨论】：