django-orm

I do have the two models below. So I'm trying to get all the modules of a particular course. As you can see, I'm already getting that particular course. So I just need to get the modules from it. I read the docs about filtering a ManyToManyField but still couldn't make it work. I know that maybe it's too simple but can't solve it. models.py class Course(models.Model): name = models.CharField(max_length=100) modules = models.ManyToManyField('Module', blank=True) class Module(models.Model): code = models.CharField(max_length=10, unique=True) name = models.CharField(max_length=65) year = models

My model in Django ORM is this class Test(Modelbase): id = models.IntegerField(null=True, blank=True) amount = models.CharField(max_length=255) I want to add the amount for list of id's. The only problem is the amount field is CharField . How do I apply sum for the amount field? Test.objects.filter(id__in=[1,2,3]).aggregate(Sum('amount')) I am using Django=1.9.1 for this. you can try do annotate with cast : from django.db.models import FloatField from django.db.models.functions import Cast Test.objects.filter(id__in=[1,2,3] ).annotate(as_float=Cast('amount', FloatField()) ).aggregate(Sum('as

How to perform a multiple column group by in Django? I have only seen examples on one column group by. Below is the query i am trying to convert to Django ORM. SELECT order_id,city,locality,login_time,sum(morning_hours),sum(afternoon_hours),sum(evening_hours),sum(total_hours) FROM orders GROUPBY order_id,city,locality,login_time` Shubhanshu from django.db.models import Sum Your_Model.objects.values('order_id', 'city', 'locality', 'login_time').order_by().annotate(sum('morning_hours'), sum('afternoon_hours'), sum('evening_hours'), sum('total_hours')) I hope the above code snippet helps (While

I have following application: from django.db import models class Worker(models.Model): name = models.CharField(max_length=60) def __str__(self): return self.name class Job(models.Model): worker = models.ForeignKey(Worker) is_completed = models.BooleanField() I want to annotate Workers query with count of completed jobs. I'll try to do it with following script: from myapp.models import Worker, Job from django.db.models import Count w = Worker.objects.create(name='Worker1') Job.objects.create(worker=w, is_completed=False) Job.objects.create(worker=w, is_completed=False) Job.objects.create(worker

I am trying to run an aggregation query that is roughly equals to: select sum(impressions) as impressions, sum(clicks) as clicks, sum(clicks)/sum(impressions) as ctr from stats group by product order by ctr; The database used is PostgreSQL. I made this query expression (Django 1.9): Stats.objects.values('product').annotate( impressions = models.Sum('impressions'), clicks = models.Sum('clicks'), ctr = models.ExpressionWrapper( models.F('clicks')/models.F('impressions')), output_field = models.FloatField() ) ).order_by('ctr') There are 2 problems with it: ctr is 0.0 because it divides integers

I'm experiencing a weird problem which I hope someone in here may be able to shed some light on. I'm overriding the save() method of a model to add some values to a ManyToMany-field after running super(). My problem is that when I'm saving in Django admin the values seems to get added to the relationship but is then empty again. If however I do it from manage.py shell it works without problem. I've put two print statements in there and they produce the exact same output regardless of if I'm running it via Django admin or via shell. class Store(models.Model): holidays = models.ManyToManyField

I want to create some part of Django ORM filter query dinamicly, now I can do: if some: Obj.filter( some_f1=some_v1, f1=v1, f2=v2, f3=v3, f4=v4, ... ) else: Obj.filter( f1=v1, f2=v2, f3=v3, f4=v4, ... ) I want something without code duplicate like this: Obj.filter( Q(some_f1=some_v1) if some else True, # what to use instead of True? f1=v1, f2=v2, f3=v3, f4=v4, ... ) Here's a hacky way to get an always true Q object: always_true = ~Q(pk=None) This depends on the fact that the primary key cannot be null. Try this; conditions = {'f1':f1,'f2':f2, 'f3':f3} if some: conditions['some_f1'] = some_v1

Possible Duplicate: A left outer reverse select_related in Django? A BlogPost has many Comment s. I want to get a list of BlogPost s and all their comments. Thus, I have BlogPost.objects.filter(my_filter).select_related() But the ForeignKey is on the Comment , not the BlogPost , so the select_related() doesn't prefetch any comments. Is there a way to get this to work? I can't reverse the query ( Comment.objects... ) because then the other objects that the select_related() does fetch wouldn't work. I need it to work both ways. Why won't you fetch the comments and then use regroup template tag