You’d probably be surprised that this is one of my most used functions within a dashboard. It is just such a cool
function. Though, it is almost exclusively used for UI/UX functionality.
“Only” is an aggregation function that can be used on a string field. If a single result comes back it will return the
result, if more than one values occur it returns null.
One of the best features is that you can use set analysis with it, which gives you a lot of control. It can be used
to pull out expression definitions stored in a field, used to create dynamic labels, and many other things.