(ANDROID) Set up a database using pure Java and SQL?

I am creating an online app where people can add friends, view their pictures and stuff. I read up on using SQLite in Android but found out that this wasn't what I needed, because it makes a specific database for each device, as opposed to a generic database that can be accessed from multiple devices.

I have only found tutorials online that include using a web server and PHP. I have 0 PHP knowledge but am very comfortable with Java and studied SQL. Would I be able to set up this database using just Java and SQL? For now I simply want to be able to register a user by username, email, and password - and sign them in using their username and password.

If anybody can point me to a good tutorial or give me a quick guide I would be really grateful.