See the attached image for a yes/no column easily updated by an EM program manually and/or automatically at Startup if a particular book has any Entity Type with a matching Entity Value already created as an Entity.
#18 is the yes/no CC table.
The code is just for Author, but checking for all Entity Types that exist in the the _entities table is trivial.
Code:
UPDATE custom_column_18 SET value = 1
WHERE custom_column_18.book IN
(SELECT book FROM books_authors_link WHERE author IN
(SELECT id FROM authors WHERE authors.name IN (SELECT value FROM _entities WHERE type = 'Author')));
UPDATE custom_column_18 SET value = 0
WHERE custom_column_18.book NOT IN
(SELECT book FROM books_authors_link WHERE author IN
(SELECT id FROM authors WHERE authors.name IN (SELECT value FROM _entities WHERE type = 'Author')))
The only decision that each user would need to make is whether they want a single yes/no table for each Entity Type, or just one per book if there is any Entity Match among any of each book's metadata.
DaltonST