How do I show the null value in the list box

[avastani]

I have two field linked to each other by an ID, but there are instances where there are null for a value in listbox A.

How can I make the listbox B show null values so that the user can select show all value in A that have nulls in B.

[#2]

Null is an undefined value so you need to create a 'dummy' to represent it. Assuming column 'a' is the field for listboxA and column 'b' is for listboxB and 'ID' is what links them:

[tab1]:

Load ID, a, x From ...;

[tab2]:

Load ID, ID as tID, b, y, z From ...;

Concatenate (tab2) Load ID, 'No value' as b

resident tab1 where not exists(tID, ID);

Drop field tID;

Regards,

Gordon