First, shout-out to all the participants in this thread, without whom this database wouldn't exist.
Shout-out to @claassen: if it weren't for your database file, this one wouldn't exist either. Especially since most of the structure was lifted straight from his database, so I take no credits for the rule set!
What is this database?
Dutch leagues down to level 7, with working periods and playoffs as well as I could. Zondag and Zaterdag clubs should be correctly separated.