Django ORM: How to compare concatenated columns?

I’m working on a Django project and I need help with a specific database query. My model has three fields: first_part, second_part, and full_text. I want to find all records where full_text is not equal to the combination of first_part and second_part.

In raw SQL, it would look like this:

SELECT * FROM my_table WHERE full_text != CONCAT(first_part, second_part)

But I’m not sure how to translate this into Django’s ORM. I know about filter() and exclude(), but they usually work with fixed values, not comparisons between columns.

Is there a way to do this comparison using Django ORM? I’d prefer not to use raw SQL if possible.

Thanks for any help or suggestions!

Ooh, interesting question! Have u tried using F() expressions? They’re super cool for comparing fields. maybe something like:

MyModel.objects.exclude(full_text=Concat(‘first_part’, ‘second_part’))

Not sure if that’d work exactly, but it mite be a good starting point. wat do u think? Has anyone else tried somethin similar?

Here’s an alternative approach that might suit your needs. You can use the ExpressionWrapper and Value classes to ensure proper type casting while performing the concatenation. For example:

from django.db.models import ExpressionWrapper, Value, CharField, F
from django.db.models.functions import Concat

MyModel.objects.annotate(
    combined=ExpressionWrapper(
        Concat('first_part', Value(''), 'second_part'),
        output_field=CharField()
    )
).exclude(full_text=F('combined'))

This method creates an annotated ‘combined’ field and then excludes records where full_text matches this field. It proves particularly useful when different field types are involved or when further operations on the concatenated result are needed.

hey, i’ve dealt with this before! u can use annotate() and then filter(). try this:

MyModel.objects.annotate(combined=Concat(‘first_part’, ‘second_part’)).filter(~Q(full_text=F(‘combined’)))

this should grab all records where full_text isnt the same as first_part+second_part. lemme kno if it works!