How to filter empty or NULL names in a QuerySet?

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.}

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.

1. When using exclude, keep the following in mind to avoid common mistakes:

Should not add multiple conditions into an exclude() block like filter(). To exclude multiple conditions, you should use multiple exclude().

Example: (NOT a AND NOT b)

Entry.objects.exclude(title='').exclude(headline='')

equal to

SELECT... WHERE NOT title = '' AND NOT headline = ''

======================================================

2. Only use multiple when you really know about it:

Example: NOT (a AND b)

Entry.objects.exclude(title='', headline='')

equal to

SELECT.. WHERE NOT (title = '' AND headline = '')

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