There's actually a database ER diagram on the Codex that you can reference if you're ever not sure if a table/column is part of the core.

This can save you some hassle, and it's also an interesting way to see how all the tables connect in the backend.

Here's the codex page that has the 2.7 database diagram (as far as I know there aren't any major differences between the 2.7 and 2.8 DB).