All fields should have (default) values.
So how do you represent unknown values? By using a default "UNKNOWN"?

Then I might just as well use a NULL...

If I insert an empty string into a varchar field in Oracle, it helpfully inserts a NULL instead.
VARCHAR-fields do in theory exist in Oracle but nobody uses them.

You are talking about VARCHAR2-fields and for them an empty string IS a NULL. There is no difference at all. If you use that data-type you must be aware of this.

In reply to Re^2: "undef" is not NULL and what to do about it by morgon
in thread "undef" is not NULL and what to do about it by Ovid

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