Question

我有3个型号： -

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

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

class ShipmentPPTLMapping(models.Model):
    pptl_id = models.CharField(max_length = 255)
    time = models.DateTimeField(auto_now = True, auto_now_add = True)
    shipment_id = models.ForeignKey('Shipment', related_name = 'pptls')

我想获取已关闭的行李的数量。

最初我有pptl_id。因此，我从shipment_id模型获取ShipmentPPTLMapping，然后使用ShipmentBagSealMapping查询shipmen_id模型。

以下是我所做的： -

bags_closed = len（Shipment.objects.filter（bags_ status _exact ='close'，bags_ time _range = [start_time，end_time]，pptls__pptl_id__exact = pptls.pptl_id ））

问题是因为每个包都可以有多个货物，因此根据我的查询，我能够得到所有关闭货物的数量。我想添加另一个过滤，例如bags_value = distinct

类似

bags_closed = len(Shipment.objects.filter(bags__status__exact = 'close', bags__time__range = [start_time,end_time],pptls__pptl_id__exact = 147)).**bags_seal = distinct**

问题2

另外，我需要获取last_bagged_on参数，该参数为我提供了最后一个关闭的行李的时间。显然，此字段将从ShipmentBagSealMapping模型中获取，但我当前的对象是模型Shipment。

如何关闭最后一个包？

这样的事情： -

last_bagged_on  = Shipment.objects.filter(bags__status__exact = 'close', bags__time__range = [start_time,end_time],pptls__pptl_id__exact = pptls.pptl_id)[0].**bags_time**

Answer 1

第一

len（queryset）是一种计算对象的坏方法。请改用.count()

bags_closed = Shipment.objects.filter(bags__status__exact='close', 
                                      bags__time__range=[start_time,end_time],
                                      pptls__pptl_id__exact = 147)\
                              .distinct('bags').count()

第二

last_bagged_on = ShipmentBagSealMapping.objects.filter(
    status__exact='close',
    time__range=[start_time,end_time],
    shipment_id__pptls__pptl_id__exact=pptls.pptl_id)[0]

如果你正在使用Django 1.6，你应该使用last_bagged_on = ShipmentBagSealMapping ... first（）而不是[0]

如何在Django模型中获得唯一值？

1 个答案:

第一

第二