If each type of Note is unique for an entry, then encapsulating your calculated field using MAX() would do the trick.
MAX (CASE WHEN .... ELSE .... END)
Thank you for this feedback,
MAX() do not work with text field, I get an error when I tried your solution,
I believe there is a known error with the current version of smart reporting when trying to use Max() on anything other than a number.
Please check with BMC on the same, as the version that we are using supports such use case with text fields too.
Is it possible to have more than one note of the same type attached to the same incident? That would complicate matters.
Otherwise, if you define separate calculated fields for each type of note using something like MAX (CASE WHEN Note type = <note type> THEN 1 ELSE 0 END), you should be able to use them to decide whether to show contents of appropriate note or use placeholder for unused note.