You're doing great! Now that you know the basics, we will examine some real-world examples of recursion. Let's say we have a company with a hierarchical structure, i.e. each employee has a superior (except for the boss). Each employee has precisely one superior, but one superior may supervise multiple employees. An example structure may look like this: In computer science, we call such a structure a tree, where each node (employee) has a parent node (superior), except for the root (boss), which has no parent node. How can we store these hierarchical relations in a database? It's quite simple: each employee is represented with a row that has a columnsuperior_id with the ID of their superior. Check out theemployee table to see what we're talking about.