CODEWITHSUNDEEP
djangodjango-models
Neeraj Kumar
Neeraj Kumar

Reputation: 533

Django Models : How to update value if case matches else keep the current value

I want to perform an update operation on a Django queryset conditionally such that the value of an attribute is updated only when it matches a condition otherwise keep the value it is currently having.

I know that conditional updates in django are performed using Case, When, then, default but not getting how to keep the existing value for the default case. I tried leaving default from the query but then it throws an error.

I want something like the following. Say there are 4 types of schemes: PRO, REGULAR, HOME, FREE.

Customer.objects.filter(age__lte=18)\
                .update(type=Case(When(type=HOME,                
                                       then=FREE),
                                       default=<keep current value>),
                        subscribed=False)

Upvotes: 0

Views: 1349

Answers (1)

Neeraj Kumar
Neeraj Kumar

Reputation: 533

Okay so I can use a F() object for it. eg. F('field_name')

So, the query I need becomes:

Customer.objects.filter(age__lte=18)\
                .update(type=Case(When(type=HOME,                
                                       then=FREE),
                                       default=F('type')),
                        subscribed=False)

Upvotes: 1

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