Working with NULL in set expression wont be that easy, since you can not make selections on NULL values in QlikView. Compare with adding a field containing NULL values in a list box, it is not possible to select NULL in such a list box.
The easiest way to include/exclude NULL in your caluclation is likely to use an IF statement and the IsNull() function. It is a bit unclear in which way you want to exclude the NULL values, so there are two approached to this as far as I can tell.
First, is if you want to exclude the Dimension related to NULL procedures. This would automaticaly also exclude the NULL values from the expressions. If so, add the Dimension as a calculated dimension instead for example like below;
=if(not isnull(Procedure), Consultant)
Second, you want to exclude the NULL values from your expression aggregations. It could look something like;
=Count(if(not isnull(Procedure), [Episode ID]))
A more sofisticated solution would be to change your script, to add a flag the NULL values. There after you could use this flag in set expressions.
Script addition could be like;
Episodes:
Load
*,
if(isnull(Procedure), 1, 0) as ProcedureIsNullFlag
;
LOAD autonumber(replace("episode_id",':','-'), 'EP') as %Episode_ID, replace("episode_id",':','-') as [Episode ID], /.../
