Autour du SIGB Koha

Comment savoir si un champ de la notice d’exemplaire non lié à un champ Koha est vide ?

Exemple sur le 995$l (et oui… curieusement on interroge le 999)

SELECT
items.barcode,
biblio.title,
biblio.author,
(SELECT description FROM itemtypes WHERE itemtype=itype) as typedoc,
(SELECT lib FROM authorised_values WHERE category='statut' AND authorised_value=notforloan) As statutencours
FROM items
LEFT JOIN biblioitems on (items.biblioitemnumber=biblioitems.biblioitemnumber)
LEFT JOIN biblio on (biblioitems.biblionumber=biblio.biblionumber)
WHERE ExtractValue(more_subfields_xml,'//datafield[@tag="999"]/subfield[@code="p"]') IS NULL
ORDER BY items.notforloan asc, itype asc