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

Use Doctrine's is empty

It's specifically designed to check for empty associations:

$qb->select('m')->from('DeliveryMethods', 'm')->where('m.countries is empty')

See: Doctrine 2 ORM Documentation: Doctrine Query Language (search for "is empty")

Answer 2

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

Answer 3

Can't join NULL values, IIRC. Apologies for the typo on twitter, should have said "can't".

Answer 4

What about this? Assuming $qb is your query builder instance

$qb->select('m')
   ->from('DeliveryMethods','m')
   ->leftJoin('m.countries','c')
   ->having('COUNT(c.id) = 0')
   ->groupBy('m.id');

This would give you the DeliveryMethods which is associated with countries and count of the associated countries is 0