Not telling you anything you probably don't already know, but most QR scanners on phones generate an "internet address" and pass it on to a browser session. Easiest to ride the horse in the direction it is going.
So if you had a local web server, accessible over your local network, you could have it serve up a database view / edit screen to display in the phone's browser session.
Is your database and possible server located in the same facility, in the same set of IP addresses?
No I cannot help with developing your app. Just trying to get juices flowing.
David A. Smith