So, I've been offered an opportunity for an internship with a software company. I think they make mobile phone applications, and I know "database" was thrown around a lot too. I'm still waiting on the details, but it's definitely .NET and C-family related stuff. I'll ask for people's experiences once I know what the actual software is.
I'm also using for free the study materials my uncle got from a stupidly expensive service certification college. I'm studying the CompTIA A+ stuff right now. It's presented in video form by Mike Meyers, meaning my uncle basically paid twenty grand for the extended version of a YouTube series. It's supposed to be a ground-up course assuming no real prior computer expertise. However, the first module is aimed at the business of being a technician, and the first couple videos are about hygiene and presentation. "As nerds, these are not our strong points."
Android is programmed with Java.
iOS is programmed with Objective-C.
Windows Phone, not sure, but I could see it being .NET.
I know nothing of Windows Phone, but if you're using C for mobile applications, I would guess they're talking about Objective-C to code for Apple iOS devices. You don't use C on Windows Phone, do you?
For databases...might want to brush up on your SQL DBMS's. For mobile...it depends whether the DBMS is on the device or a server the device connects to. If it's on the device, it's probably SQLite. If it's on a server, it could be any number of things...Oracle and MySQL being the most common.
You'll have to let us know what you're actually doing. I'm decent at mobile application development and I'm actually very good at designing databases.