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I have a model that looks like this:
Requests: user, req_time, req_text In the DB, the records can look like this:
id, user_id, req_time, req_text 1 1 TIMESTAMP YES 2 1 TIMESTAMP NO 3 2 TIMESTAMP YES etc.
How do I write a Django ORM query that: groups the Requests by user, filters the Requests based on req_text, and also, select the max id of the resulting result set. So for each user, I will return one row which matches the filter condition and also has the greatest id.
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Unlike aggregate() , annotate() is not a terminal clause. The output of the annotate() clause is a QuerySet ; this QuerySet can be modified using any other QuerySet operation, including filter() , order_by() , or even additional calls to annotate() .
Django Field Lookups Managers and QuerySet objects comes with a feature called lookups. A lookup is composed of a model field followed by two underscores ( __ ) which is then followed by lookup name.
to Django users. According to the documentation on models. OuterRef: It acts like an F expression except that the check to see if it refers to a valid field isn't made until the outer queryset is resolved.
Aggregate Aggregate generate result (summary) values over an entire QuerySet. Aggregate operate over the rowset to get a single value from the rowset. (For example sum of all prices in the rowset). Aggregate is applied on entire QuerySet and it generate result (summary) values over an entire QuerySet.
from django.db.models.aggregates import Max request_values = Requests.objects.filter(req_text='YES') \ .values('user') \ .annotate(max_id=Max('id')) Then request_values will look like this:
[ {'user': 1, 'max_id': 1}, {'user': 2, 'max_id': 4}, {'user': 3, 'max_id': 5}, {'user': 4, 'max_id': 12}, ... ] If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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