There’s a lot more to T-SQL. Things like Dealing with the Database Administration. For example Security, backup and restores. Or other things, like creating User Defined Functions, Views, Triggers, Stored Procedures, Extended Stored Procedures User-Defined Stored Procedures, SQL Mail. All of these other elements of the language have been omitted here. This is because I am trying to focus primarily on data manipulation. Working with Column-Row-Relational data. Playing around with it, and analysing it. Making it more useful for what used to be called “Business Intelligence”. The current buzzword for it is “Insight”.
Become good at a skill, and you get to have a feel about how to use it to solve a situation, even before you fully understand the situation. This is a level of competency I call an expert level. You become so good at what you do, you develop a third sense. And it becomes your initial way into what you do. This is the Advanced Stuff. It comes with years of experience.