I've queried all children of the post, and two records are shown. This is ok because there are 2 images in the gallery, but I can see no field in the database which makes it clear which one is the featured image.
I have joined the wp_postmeta table also, but there is no meta_key which indicates which of the 2 is the featured image.
Note: I do not want to look in the admin panel, I need a programmatic way to determine from the current database setup.
Does anyone know how the system knows which is the featured image in the db?