How to represent a table with several one-to-many relationships

Question

I have a table, A , whose rows have a many-to-one relationship with several other tables. The rows in the other tables-- B , C , D --each have many A s. Each A relates exclusively to another table. For example you never have an A that relates to both a B and C .

Currently, the A table is represented as a "flattened" sum-type where each row has a nullable AId , BId , CId , & DId . The "parent" of any given row in A is determined by which one of these FK's in non-null.

This has been working fine so far. However, I have several new features to be implemented down the road which will also have many A s.

My question is: is there a more extensible design than simply adding more columns to store FK's to these other tables?

Answer 1

You have a type of MUCK (massive unified code key)table, but only worse.

Instead of a table like this:

MUCK(aid, bid, cid, did, value1)

It would work better like this:

MUCK(table, id, value1)

The table is a,b,c, or d (or so on) and the id is the id within that table.

However, I really suggest you do some research on why MUCK and EAV tables can be a nightmare as you add requirements and features.

Here is a question I recently answered and a link to another that discusses why EAV (and even more, MUCK) is not always the best idea.

How to store custom entity properties in a relational database