Are you kidding me? It does happen occasionally. I'm guessing you haven't been a developer for very long if you've never run into this. The fact that abstraction libraries and ORMs exist in the first place suggests that it's a real problem.

My comment was based on my own experience having to move a PHP app from SQL Server to Oracle. And it was just about the last app I'd ever expect to have to move from one database to another.

I'm not sure why my original comment was modded down because it's just plain common sense. With all the libraries out there for abstracting database access and ORMs you're just begging for trouble if you still use the database specific stuff. Unfortunately, in my case none of that stuff was available yet.