If the http://db.kreie.net URL doesn't work, go to this website to access the scripts and other files used in this video series. https://sites.google.com/view/db-krei...
See the different ways to join two tables together: inner join, left one-sided outer join, right outer join, full outer join. The error “column ambiguously defined” is also shown and the need for a fully qualified column in some situations.