SetNull() in a Nullable field conundrum

[blewip]

This may be a stupid question however; if I have a Nullable field (say varchar(12)), why cannot I set the derivation to SetNull()?

Surely if a field is nullable it can accept a Null, as a value. And setNull surely sets Null to be the value?

[blewip]

I am going to Sequential Stage, so I can set Null field value = "" in Format, Field Defaults it does kind of work.

However if I was going to other stages I may not have this option.

I shall try this out.