I think there is an issue with Lesson 4.

At 6:38, you joined EmployeeT.Department with DepartmentT.DepartmentName. (Fig. 1)

At 9:22, you deleted EmployeeT.Department

Deleting EmployeeT.Department would break the update query. I understand that you may only want to run the query once and then delete it without even saving it. But if I want to save it and open it in the future, just to recall what I was doing, I wouldn't be able to do it. The query can't even be opened in the Design View. I would get an error message.