Ok, this one is seriously baking my noodle.
I’ve got a custom post type of “Program” and a custom post type of “Venue”.
These are joined by a relationship field on the Program post type called “Location”.
I want to query WordPress to find only the Venues that are attached to a Program. I think I could do it via the posts_where filter but I can’t figure out how to write the MySQL statement to get the venues.
You should just be able to say get_field( 'location' )
when listing out your programs and it should return an array of IDs or Post Objects (depending on the return value you selected for the Relationship field).