Question

I’m making a review type website, and I would like for there to be 2 types of users. One would be the majority, reviewers while the other would be the person the review is about. How, in terms of database design would I differentiate the two. Should I have separate tables for reviewers and reviewies or simply assign a different range of ID’s for both?

Answer 1

This is a classic super-type/sub-type situation. Users and Reviewers are both people, and relational bigots would say you should have one “people” table containing all of the common person fields. You can then have explicit one-to-one foriegn key relationship to a reviewers table, which contains the reviewer-specific fields and related keys to other reviewer-specific tables. You check to see if a person is a reviewer by joining to the Reviewers table.

You can of course add other types of people with different data to this approach. This is a good way to model things for relational bigots like me who like to avoid null-valued fields and undeclared foreign keys that reference one of several tables. MySQL jockeys would just cram it all into one big table with lots of nulls, magic numbers, and comma-separated lists in varchar fields.

If you know the requirements will not change in the future (ha!), and there is no difference in schema between users and reviewers, just use a single person_type field and keep it simple.

Never use “key ranges” for any reason. That’s just hackery which will only cause a massively painful recoding effort for you or someone else in a few years. Primary keys should be without semantics and invariant.