Thank you, Docpuddu. It is more than what I need, and a nice article indeed.
One more thing I need to add, of which I searched from the community, is that my timestamp even though Load as Date, the Date gives multiple records for the same date, and I need to use this script expression to Load the Date:
Load Date(Floor(Date(timestamp))) AS Date
I wonder if simply use: Load Date(timestamp) AS Date
the system will still keep the time portion of the timestamp in the Date field and show multiple records for the same date ??