Django queryset filtering

[mtp...@gmail.com]

I have a queryset that returns all the expired licenses objects as shown below.

qs = LicenseIssue.objects.filter(expiry_date__lte=TODAY).order_by('-expiry_date')    

Here is my situation:

There exists multiple issued licenses of different businesses for year 2020 and their  previous issued licenses for the for year 2019, 2018 and so on. The above queryset results to listing all expired licenses though I'd like to make it possible if there exists issued licenses for year 2020 their previous issued licenses should not appear in the expired licenses queryset. Please advise on this.

[Oleg Kishenkov]

Hello, use a filtering chain, a refined queryset is itself a queryset so you can filter it further. Also, Django has extensive lookup support in its filtering methods. Let's assume LicenseIssue is related to Business as many to one (it is probably the case):

class Business(models.Model):

    name = models.CharField(max_length=15)

class LicenseIssue(models.Model):

    expiry_date = model.DateField(null=False)

    business = model.ForeignKey(Business, on_delete=models.CASCADE)

First you filter out expired licenses, second you exclude the licences which belong to businesses that have valid licences.

qs = LicenceIssue.objects.filter(expiry_date__lte=datetime.now()).exclude(business__license__expiry_date__gte='2020-01-01')

I have to point out that here license in business__license__expiry_date__gte is an automatically generated related_query_name.

Oleg

чт, 25 июн. 2020 г. в 01:25, mtp...@gmail.com <mtp...@gmail.com>:

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[Dan Madere]

I'd make two queries. One to see which businesses currently have active licenses, then a second to get the expired licenses, excluding the businesses from the first query. Here's some example code, assuming the LicenseIssue model has a "business" foreign key field:

active_business_ids = LicenseIssue.objects.filter(expiry_date__gt=TODAY).values_list('business_id', flat=True).distinct()

expired_licenses = LicenseIssue.objects.filter(expiry_date__lte=TODAY).exclude(business_id__in=active_business_ids).order_by('-expiry_date')

[mtp...@gmail.com]

Thanks guys this was very useful 

[Dvs Khamele]

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