--- In firebird-support@yahoogroups.com, Helen Borrie <helebor@t...>
wrote:

> At 11:51 PM 27/01/2004 -0200, you wrote:
> EXTRACT() can't do anything with NULL ("expression evaluation not
> supported") so don't write queries that pass NULLs to EXTRACT().

Helen, IMO this limitation is'nt conditioned by some principle, just
"this is the way it is". Particularly knowing that null stored in
existing row is'nt a problem for Extract. I believe Dmitry will take
care of it before release.

> What is the problem you want to solve? Do you want to find a way to
> prevent EXTRACT() being called if there is a null there? If so, try

using

> CASE().

IMO this is today's workaround for Extract problem.

Best regards,
Alexander