You can able to do like this also.
select OEORI_Date, OEORI_TimeOrd, OEORI_UpdateDate, OEORI_UpdateTime,
datediff('n',%EXTERNAL OEORI_Date||' '||%EXTERNAL OEORI_TimeOrd,%EXTERNAL OEORI_UpdateDate||' '||%EXTERNAL OEORI_UpdateTime)
from SQLUser.OE_orditem
