Possible to join different entity type on using EntityFieldQuery?

Question

I am wondering whether I can use EntityFieldQuery to fetch all entities belonging to a specific content type. This entity type has a reference to another entity type. Is it possible to check against the refereed entities fields in the same query?

Answer 1

No.

An EntityFieldQuery allows you to run queries based on field and property conditions, but it has no way to query the fields or properties of a referenced entity.

Such a thing would involve some pretty full on logic, and it probably wouldn't even be possible to provide a programmatic interface to it that made sense.

Answer 2

What you would need to do is run a query against the referenced type first so you have all the node ids that apply, then use them in a second query with a field condition like:

->fieldCondition('YOUR_REFERENCE_FIELD', 'target_id', $nids, 'IN')

This may not be practical if your database is very large.