I have various different entity types in my database. For purposes of example, consider an IMDB database:
- and 20 more tables
My application enables free-form many-many relationships between any of these entities.
What is a sane way to model this in a maintainable way?
Currently, my app uses a table with "a_id", "a_type", "b_id", "b_type". With the type identifying the table (e.g. "movie"). This means there is no referential integrity checking, which makes me uneasy.
What are the alternatives? The only one that comes to mind is to expand the linking table with a column for every other table. So I have
b_director_id. However, while this preserves referential integrity, it feels strange (I have not seen such tables before) and I suspect it would be difficult for application code to process it (it would have to have a big if-statement to check what is actually referenced).
Thus I ask for your advice - is there a convenient industry standard way to model such flexible relationships?
My database engine is is SQL Server.