can you explain more about "period_no". I'm not really understand about that. As example, I want to start at 8 am everyday and I am able to see the history of the data (> a week ago) . Much appreciate if u can help me to get better understanding.
period_no is an integer, or expression that resolves to an integer, where the value 0 indicates the day that contains time. Negative values in period_no indicate preceding days and positive values indicate succeeding days.