You are very much welcome!
I would recommend you to not try to think too much SQL when working with the Progress database - it is not an SQL database in the first place and there many differences between SQL and the Progress ABL. Most prominently the ABL is record oriented whereas SQL is result set oriented.
In the past when I was still running Progress related trainings I always suggested my students to empty their bottle so that there is room for something new.
Heavy Regards, RealHeavyDude.