As part of our mass meta-tag burnination, we're also considering database-schema. It also seems closely related to database-design, which has been burninated and blacklisted just recently. We already have a database tag, which is not up for burnination. I don't think we need very many database-related tags since we already have a site dedicated to this: Database Administrators. I'm also thinking that it may slightly reduce the chances of receiving questions solely about databases (no code), which will get migrated to Database Administrators anyway.
No, we don't. Merge them into database I say.
I just don't really see a need. There is a whole SE site dedicated to DB Administration, and schema-design/database-design is more looking at charts and concepts than code generally.