Hi, I am a primarily self taught developer and beside some of the old school reference books that were the mainstay of learning software development and server management I would say W3 Schools has a very could basic tutorial. If you are wanting to take people who have some basic understanding and advance them in their skills then some SQL specific classes on udemy or skill share is a good starting point. For even more advanced learning you really need to get into platform specific training such as from Oracle, Microsoft, or your platform of choice. I would be happy to discuss more options and understand your desired outcome over a call.