Bug in preview feature "Explicit Column Selection"
I've found two situations where this doesn't work as you'd expect. No solutions necessary as the workaround is straightforward, just recording as a bug. I am working with SQL Server as datasource.
1. ClearCollect from table/view and only use returned column of interest as a dropdown source for items. The collection will have correct number of rows returned, but will not display the data in the dropdown.
2. ClearCollect from a table/view and only use returned column of interest in a conditional statement. Again, rows are returned to collection but data in rows are empty, so formula will fail.
Solution is easy: just force the collection to load properly using a hidden control and reference the column you want directly e.g. use a label and set text property to "First(myProblemCollection).MyProblemField" and it should populate the next time you load the app.
OK, looks like I was wrong - the trick of forcing the problematic column appears to only work in the browser, and not on either Android or iOS apps. So I've had to turn this feature off, which I am concerned with as I don't have any power over when it will be moved to production and therefore be on whether I like it or not. I would appreciate some feedback from an MS admin here.