Hi Somnath,
up to SPS 8 SAP HANA does not provide the feature to restrict trigger actions for specific columns.
We don't state that we do so in the documentation. Instead it is pretty clear that the current trigger option is a rather simple tool (especially compared to other trigger implementations).
AFAIK a feature like column-specific trigger actions might be included in later releases - but as usually, we will have to wait until the feature is actually available.
Until then, you could go on and manually check for changed values in the columns you are interested in.
- Lars