Questions tagged [django-models]

For questions concerning use of the model class from the web framework Django.

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1184votes
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What is the difference between null=True and blank=True in Django?

When we add a database field in django we generally write: models.CharField(max_length=100, null=True, blank=True) The same is done with ForeignKey, DecimalField etc. What is the basic difference in ...
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843votes
17answers
536kviews

How do I do a not equal in Django queryset filtering?

In Django model QuerySets, I see that there is a __gt and __lt for comparative values, but is there a __ne or != (not equals)? I want to filter out using a not equals. For example, for Model: bool ...
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  • 42.1k
751votes
10answers
756kviews

How can I temporarily disable a foreign key constraint in MySQL?

Is it possible to temporarily disable constraints in MySQL? I have two Django models, each with a foreign key to the other one. Deleting instances of a model returns an error because of the foreign ...
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  • 34.8k
712votes
13answers
227kviews

What is a "slug" in Django?

When I read Django code I often see in models what is called a "slug". I am not quite sure what this is, but I do know it has something to do with URLs. How and when is this slug-thing supposed to be ...
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  • 18.7k
611votes
11answers
372kviews

What does on_delete do on Django models?

I'm quite familiar with Django, but I recently noticed there exists an on_delete=models.CASCADE option with the models. I have searched for the documentation for the same, but I couldn't find anything ...
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544votes
9answers
419kviews

How to filter empty or NULL names in a QuerySet?

I have first_name, last_name & alias (optional) which I need to search for. So, I need a query to give me all the names that have an alias set. Only if I could do: Name.objects.filter(alias!="") ...
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  • 16.3k
521votes
11answers
161kviews

What's the difference between django OneToOneField and ForeignKey?

What's the difference between Django OneToOneField and ForeignKey?
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  • 7,895
511votes
15answers
281kviews

Extending the User model with custom fields in Django

What's the best way to extend the User model (bundled with Django's authentication app) with custom fields? I would also possibly like to use the email as the username (for authentication purposes). ...
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  • 16.8k
502votes
4answers
169kviews

How to define two fields "unique" as couple

Is there a way to define a couple of fields as unique in Django? I have a table of volumes (of journals) and I don't want more then one volume number for the same journal. class Volume(models.Model):...
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431votes
12answers
417kviews

How to query as GROUP BY in django?

I query a model: Members.objects.all() And it returns: Eric, Salesman, X-Shop Freddie, Manager, X2-Shop Teddy, Salesman, X2-Shop Sean, Manager, X2-Shop What I want is to know the best Django way ...
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  • 33.3k
417votes
3answers
215kviews

What's the difference between select_related and prefetch_related in Django ORM?

In Django doc, select_related() "follows" foreign-key relationships, selecting additional related-object data when it executes its query. prefetch_related() does a separate lookup for each ...
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  • 15.2k
405votes
9answers
434kviews

How to delete a record in Django models?

I want to delete a particular record. Such as delete from table_name where id = 1; How can I do this in a django model?
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  • 9,773
385votes
16answers
276kviews

Convert Django Model object to dict with all of the fields intact

How does one convert a django Model object to a dict with all of its fields? All ideally includes foreign keys and fields with editable=False. Let me elaborate. Let's say I have a django model like ...
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  • 30.5k
374votes
15answers
202kviews

Can "list_display" in a Django ModelAdmin display attributes of ForeignKey fields?

I have a Person model that has a foreign key relationship to Book, which has a number of fields, but I'm most concerned about author (a standard CharField). With that being said, in my PersonAdmin ...
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  • 14k
367votes
5answers
281kviews

Django Model() vs Model.objects.create()

What it the difference between running two commands: foo = FooModel() and bar = BarModel.objects.create() Does the second one immediately create a BarModel in the database, while for FooModel, the ...
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