Edge detection for discrete tags

Edge detection for discrete tags operates differently than for analog tags. For example, assume the following discrete tags are stored.

A representation of the data stored in the system is as follows:

The following queries select values of "SysPulse" and "MyPulse" that have a value of 1 (On) from the History and WideHistory tables between 12:59 and 1:04 a.m. on December 8, 2001. No edge detection is specified.

This is a query of the History table:

SELECT DateTime, TagName, Value

FROM History

WHERE TagName IN ('SysPulse','MyPulse')

AND DateTime > '2001-12-08 00:59:00'

AND DateTime <= '2001-12-08 01:04:00'

AND wwRetrievalMode = 'Delta'

AND Value = 1

AND wwEdgeDetection = 'None'

The results are:

The following is a query of the WideHistory table:

SELECT * FROM OpenQuery(INSQL, 'SELECT DateTime, SysPulse, MyPulse FROM WideHistory

WHERE DateTime > "2001-12-08 00:59:00"

AND DateTime < "2001-12-08 01:05:00"

AND SysPulse = 1

AND MyPulse = 1

AND wwRetrievalMode = "Delta"

AND wwEdgeDetection = "None"

')

The results are: