I'm not a database guru, so be patient with me: Is there some kind of "wrapper" software you can put around an SQL database (MySQL perhaps) that allows you to internally configure database rules on a higher level than the database itself can actually implement? (E.g., "rows in table A can be deleted, but only if there are no related rows in table B and only if column x for the row in table A is in state y.")

The idea would be to keep from having to trust this kind of logic to the client programs, while also avoiding the need to write a full fledged server daemon just for your application. The clients submit their SQL insert requests to the wrapper daemon, and the daemon passes them on to the database if they pass a rules table defined for that particular database.

Again, not a database guru, but I'm sure that can't be a new idea.

You're right about the new idea thing. A few quarters ago, we did the same thing with MySQL server. The exception though is that we did not program the database itself, we used a few PHP scripts to read through the database records and tables. The scripts would only run if information was entered into a form and submitted (or through a cron job, in my case). Not sure if that helps, but the scripts we made did wrap around the database.

Let me rummage through my database stuff and see if I can help you.

Unfortunately, I couldn't find anything useful for what you wanted to do. Are there any database admins out there who know more than I do?

You can try to use triggers in mysql itself.

See e.g. http://www.brokenbuild.com/blog/2006...ith-a-trigger/ how to abort an insert, but I guess it will work similar for delete.

And obviously links about triggers.

Never used triggers, so you have to figure a few things out yourself