How to design a media table with references to multiple (at least 4) tables?

Question

I am designing a database for my cookbooks. I have created multiple tables in my design: books, authors, recipes, ingredients and for all these items I want to link media (images or video) to items in all these tables.

I was thinking of a design like:

media_id,
rid (primary key of foreign table),
rtype (1=book, 2=author, 3=recipe, 4=ingredient),
media_type(1=image,2=video),
media_url

But how will I ensure relational integrity?

Thanks

Answer 1

Your proposed design seems to imply that each entity (book, author, etc.) can have multiple media files, so to maintain relational integrity, I'd have separate junction tables for each relationship.