> As an example: a retail transaction database. Or a calendar booking system. That should be really simple, right? Just record who ordered what, when they received it, who sold it, etc. Who reserved the room, who to send invites out to, simple?

I am not sure people downvoting me understand what all goes into an EHR/practice management software. Calendar booking? Yep. Billing. Oh hell. Don't get me started on the byzantine mess that medical billing is! Then there's charts with icd-9/10 hell. And then everyone you sell it to wants their own charts a little different. Patient records, insurance, I mean, it goes on. The database had several thousand tables. It was insane.