This code removes the first two characters from the classification number and sets the prefix to ‘J’ for items in two record sets.
begin tran
update ird
set ird.ClassificationNumber = substring(ird.ClassificationNumber, 3, 99)
,ird.CallNumberPrefix = 'J'
from polaris.polaris.ItemRecordSets irs
join polaris.polaris.ItemRecordDetails ird
on ird.ItemRecordID = irs.ItemRecordID
where irs.RecordSetID in ( 229479, 229480 )
select ird.ItemRecordID
,ird.CallNumberPrefix
,ird.ClassificationNumber
,ird.CallNumber
from polaris.polaris.ItemRecordSets irs
join polaris.polaris.ItemRecordDetails ird
on ird.ItemRecordID = irs.ItemRecordID
where irs.RecordSetID in ( 229479, 229480 )
--rollback
--commit
This has been tested on Polaris 7.3.