Doctrine 2 DQL - Select rows where a many-to-many field is empty?

Question

I have two classes in this example - DeliveryMethod and Country. They have a many-to-many relationship with each other.

What I want to do is select all DeliveryMetho

Answer 1

There is no need in joins and havings. Simply use SIZE function:

$qb->select('m')
   ->from('DeliveryMethods','m')
   ->where('SIZE(m.countries) = 0');

This will give you all methods without attached countries