Hello!
Theory on Derived Tables: "~ ...when creating DTs you can define INLINE or EXTERNAL column aliases".
Practice on Derived Tables: I prefer EXTERNAL column aliases - and it works:
Theory on CTE: "~ define either INLINE or EXTERNAL column aliases".
Practice on CTE: 
I failed to define the external column alias in CTE (I tried in various ways) and did not find any example on the matter either.
How can I "define external column aliases" in CTE?
Thank you in advance,
Michael