How to maintain trend info on CITADEL SQL Query

[bruno_costa]

Hi All,
I'm using ms excel via ODBC connection to extract data from CITADEL via SQL queries. In LabVIEW DSC Module there are an option in the function "Read Historical Traces" thats maintain trend info of tag if no data is recorded in the selection time.
When i try to get CITADEL data via SQL if no data is recorded in that period the result is a blank column. How to maintain trend info or in this case?

[Mauro Vera]

Good afternoon, Bruno

Follow this link, please verify readiness if the procedure is correct if the problem persists please contact us.

Citadel Database Querying and Exporting Data to Excel
http://zone.ni.com/devzone/cda/epd/p/id/2001

Overview of Citadel Historical Database Archiving Methods
http://zone.ni.com/devzone/cda/tut/p/id/3751

Accessing Citadel 4 Data with Microsoft Excel
http://zone.ni.com/devzone/cda/tut/p/id/3813

Can I Change the Default Timeout for the Read Historical Trend (s) in DSC VI?
http://digital.ni.com/public.nsf/allkb/513C871B883E34A386256D040071C97F?OpenDocument

Sincerely,

Mauro Vera

[bruno_costa]

Thanks Mauro for the Help,

All links that you have listed, don't show how to maintain trend info. Suppose that I have a variable that's a setpoint. I had changed this setpoint at 7:00 am and later at 4:00 pm. So, citadel was recorded two point only in this period. When I try to get a interpolated data from 8:00 pm until 3:00 pm I will get a blank column for this variable. I only will have a full column if I change the start and stop time to 7:00 am and 4:00 pm that's is not correct because we have a valid value for this variable in any time between 7:00 am and 4:00 pm.

In another post I try to solve this problem using subqueries to get the last point before start time and the first point after stop time and then get a full set. But the citadel don't evaluate this query. I have tested the same query in MySQL and works fine (Can I use RawData and IntData on the same query on citadel 5? ).

Bruno B. Costa.