I need to make report to extract serials data 

but its not working

i think there is sothing wrong but i don't konow

could any body help me

select 
  ExtractValue(marcxml,'//datafield[@tag="501"]/subfield[@code>="a"]') as ID,
  ExtractValue(marcxml,'//datafield[@tag="310"]/subfield[@code>="a"]') as Freq,
  ExtractValue(marcxml,'//datafield[@tag="245"]/subfield[@code>="a"]') as Title,
  ExtractValue(marcxml,'//datafield[@tag="260"]/subfield[@code>="b"]') as Publisher,
  ExtractValue(marcxml,'//datafield[@tag="260"]/subfield[@code>="a"]') as Publication place,
  ExtractValue(marcxml,'//datafield[@tag="546"]/subfield[@code>="a"]') as Language,
  ExtractValue(marcxml,'//datafield[@tag="500"]/subfield[@code>="a"]') as Note,
  ExtractValue(marcxml,'//datafield[@tag="500"]/subfield[@code>="a"]') as Subject,
  ExtractValue(marcxml,'//datafield[@tag="982"]/subfield[@code>="a"]') as Price,
from 
  biblioitems 
where 
  itemtype = CR

Mohamed El Zalabany