I'm breaking my head trying to figure how to solve this issue.
When using SQL, If the column (property) is populated with at least one value and is a %List, then I can check if it's $listvalid and $listlength(column) > 0.
Now let's suppose there's no data inserted for that column on next row.
I can't simply use $listvalid because $listvalid("") = 1. Yeah, empty values is a $list for Caché.
So my question is, how do I discover if the regarding column is indeed a %List independently of being empty or not when retrieving it's value via SQL?

