[Koha] item copynumber NULL problem

Greetings, I'm Yared from Ethiopia, Hawassa University. I had a problem on MARC a couple of days and it was solved successfully. Now we were trying to install and us Koha 3.0.02 version on Ubuntu 8.04 LTS version for the University library information System. after a while when want to generate a guided report using the following sql statement it won't display the copynumber. the sql statement is as follow. select b.title, itemcallnumber, barcode, copynumber, i.timestamp  from biblio b, items i where b.biblionumber = i.biblionumber and homebranch ="TLIB"  and i.timestamp > "2009-10-02 14:32:17" But the copynumber does exist and is views with the catalogue view when we execute cgi-bin/koha/catalogue/MARCdetail.pl file. please help me,