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Rank: Administration
Groups: Administration
Joined: 6/20/2008
Posts: 612
Location: Cheshire, United Kingdom.
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In the previous example we showed you how to query the PI archives for values: Get Snapshot and Archive values
Following on from that example, we will switch our attention to the PI ODBC table "PIinterp" where we will retrieve an interpolated value for the passed timestamp - this is the same as PI-Datalink Archive Value function with retrieval mode set to Interpolated or PISDK.PIPoint.Data.ArcValue using PISDK.RetrievalTypeConstants.rtInterpolated.
Our only change to the previous example is to switch tables to PIinterp:
Previous SQL query: SELECT value FROM PIcomp WHERE TAG='SINUSOID' AND time =DATE('18-Nov-08 09:00')
New SQL Query: SELECT value FROM PIinterp WHERE TAG='SINUSOID' AND time =DATE('18-Nov-08 09:00')
To implement:
Code:Sub RetrieveValues()
If PIODBC_Connection Then
Dim RS As ADODB.Recordset
Set RS = New ADODB.Recordset
Set RS = Conn.Execute("SELECT value FROM PIinterp WHERE TAG='SINUSOID' AND time =DATE('18-Nov-08 09:00')")
On Error Resume Next
Debug.Print RS.Fields("VALUE").Value
If Err.Number <> 0 Then Debug.Print "No archive value exists at this time."
On Error GoTo 0
Set RS = Nothing
Else
End If
End Sub
Providing there are good values in the archives for the PI tag you will retrieve the interpolated value at the passed time.
Principal Consultant
Real-Time Data Management @ Wipro Technologies
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OSIsoft vCampus is a subscription-based, online offering that consists of providing everything people need to develop applications on the PI System. We invite you to take a "tour" of the OSIsoft Virtual Campus - also feel free to consult the FAQ or contact OSIsoft vCampus for more details.
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