Say i have itemcode,qty, unit price as column in table, and in select statement
it should possess itemcode,qty,unitprice and total an extra column
Table name potrdhd - (purchase order transaction details header table)
then
Select itemcode,qty, unitprice,(unitprice*qty) as tot from potrdhd

This will return an extra column as tot which contains unitprice* qty for each record

Regards,
ashwath