Filtering for empty or NULL names in a queryset

Filtering for 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!="")

So, what is the equivalent to the above?

Solutions/Answers:

Answer 1:

You could do this:

Name.objects.exclude(alias__isnull=True)

If you need to exclude null values and empty strings, the preferred way to do so is to chain together the conditions like so:

Name.objects.exclude(alias__isnull=True).exclude(alias__exact='')

Chaining these methods together basically checks each condition independently: in the above example, we exclude rows where alias is either null or an empty string, so you get all Name objects that have a not-null, not-empty alias field. The generated SQL would look something like:

SELECT * FROM Name WHERE alias IS NOT NULL AND alias != ""

You can also pass multiple arguments to a single call to exclude, which would ensure that only objects that meet every condition get excluded:

Name.objects.exclude(some_field=True, other_field=True)

Here, rows in which some_field and other_field are true get excluded, so we get all rows where both fields are not true. The generated SQL code would look a little like this:

SELECT * FROM Name WHERE NOT (some_field = TRUE AND other_field = TRUE)

Alternatively, if your logic is more complex than that, you could use Django’s Q objects:

from django.db.models import Q
Name.objects.exclude(Q(alias__isnull=True) | Q(alias__exact=''))

For more info see this page and this page in the Django docs.

As an aside: My SQL examples are just an analogy–the actual generated SQL code will probably look different. You’ll get a deeper understanding of how Django queries work by actually looking at the SQL they generate.

Answer 2:

Name.objects.filter(alias__gt='',alias__isnull=False)

Answer 3:

Firstly, the Django docs strongly recommend not using NULL values for string-based fields such as CharField or TextField. Read the documentation for the explanation:

https://docs.djangoproject.com/en/dev/ref/models/fields/#null

Solution:
You can also chain together methods on QuerySets, I think. Try this:

Name.objects.exclude(alias__isnull=True).exclude(alias="")

That should give you the set you’re looking for.

Answer 4:

From Django 1.8,

from django.db.models.functions import Length

Name.objects.annotate(alias_length=Length('alias')).filter(alias_length__gt=0)

Answer 5:

To avoid common mistakes when using exclude, remember:

You can not add multiple conditions into an exclude() block like filter.
To exclude multiple conditions, you must use multiple exclude()

Example

Incorrect:

User.objects.filter(email=’example@example.com’).exclude(profile__nick_name=”,
profile__avt=”)

Correct:

User.objects.filter(email=’example@example.com’).exclude(profile__nick_name=”).exclude(profile__avt=”)

Answer 6:

You can simply do this:

Name.objects.exclude(alias="").exclude(alias=None)

It’s really just that simple. filter is used to match and exclude is to match everything but what it specifies. This would evaluate into SQL as NOT alias='' AND alias IS NOT NULL.

Answer 7:

this is another simple way to do it .

Name.objects.exclude(alias=None)

References