I have done some test in SQL table. There is no prevention against duplicate in unique SQL table columns. Validate function doesn't catch the error and Errors function returns blank. At the moment the app crash with errored patch code when duplicate is added into unique column in SQL
Had some e-mail conversations with Sienna. The way to deal with errors is with the IsEmpty( Errors ( ... ) ). pattern. This works. The suggestion here was for a different way.