[Koha] Queston on itemcallnumber system preference and item call numbers in general.

[Manos PETRIDIS]

I want to comment on a couple of issues that I've encountered as it regards call numbers in koha, hoping that they may be of interest to other users as well.:

Is there a way to have complex expressions in the itemcallnumber system preference?
For example, in MARC21 I would prefer having call numbers formatted as "999.99 Aut YYYY" where 999.99 are the first five digits of DDC code, Aut are the first three characters of the soundex of Author name and YYYY is the copyright year,

I have kept the "082ab"  default value, and the items' call numbers have been created accordingly. 
While I can update the items table once, using something like the following query, this is not reftected nor in the search sesults of existing biblios, nor in newly created item records' call numbers.

UPDATE items it
LEFT JOIN biblioitems on (it.biblioitemnumber=biblioitems.biblioitemnumber) 
LEFT JOIN biblio on (biblioitems.biblionumber=biblio.biblionumber) 
SET it.itemcallnumber = 
CONCAT
(
LEFT(LTRIM(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(LTRIM(it.itemcallnumber), '''', '' ), ' ', '' ), '/', '' ), '_', '' ), '.', '' )), 3), 
'.',
SUBSTRING(LTRIM(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(LTRIM(it.itemcallnumber), '''', '' ), ' ', '' ), '/', '' ), '_', '' ), '.', '' )), 4, 2), 
' ',
LEFT(LTRIM(RTRIM(SOUNDEX(biblio.author))), 3),
' ',
CONVERT(biblio.copyrightdate, CHAR(4))
)
;

a) Does koha provide for such functionality? 
b) How may I modify my SQL statement so that it would use the 092ab entry if filled, otherwise use 082ab?
c) How may I modify itemcallnumber system preference so that it would use the 092ab entry if filled, otherwise use 082ab?
 
Kind Regards,
Manos