DAM: can not search asset with SQL2 by metadata if its data type is Long or Integer. Please help

Adobe Experience Manager, Version: 6.4.5.0

I tried to search item on one of DAM servers with sql2:

SELECT * FROM [dam:Asset] as node WHERE ISDESCENDANTNODE (node, '/content/dam/products/') and (node.[jcr:content/metadata/xmp:item-num]=12345).

If data type for xmp:item-num is string, it works fine. But if chsanging datas type to Integer/Long, return nothing. Obviously this is a system bug because the same SQL2 works on another server. How to fix trhis problem?

Thanks,

James