That depends on which tool you use for importing the data.
With a proper ETL tool like DataServices or the SP9 built-in EIM features you could add the loading date to the records.
When you stick with just loading csv files 1:1 into your database, then the calculated columns or triggers seem to be the only option to yield the effect.
If you actually want to achieve something like a data inbound layer then you may want to consider using "bigger" tools than the import command.
- Lars