How to specify null value as filter in a Doctrine query?
I use doctrine with symfony, and this is how I do:
where('a.vertical_id is NULL');
If you are using Symfony 2 and above, you can use this code:
->where($qb->expr()->isNull('a.vertical_id'));
Reference:
http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/query-builder.html#the-expr-class