Rank: Administration
Groups: Administration
Joined: 6/20/2008
Posts: 612
Location: Cheshire, United Kingdom.
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So far we have given examples of extracting data from a single table within PI but as those familiar with SQL will know, it is possible to join tables together to extract data from both tables in a single query.
Let us look at 2 tables from within PI, PIcomp (data/events) and PIpoint (tag attributes etc).
What we are going to do is retrieve the current value for the PI tag SINUSOID from PIcomp and get it's descriptor from PIpoint.
How will your SQL query look for this?
SELECT cmp.Value, pnt.descriptor
FROM PIcomp cmp, PIpoint pnt
WHERE cmp.tag = 'SINUSOID'
AND cmp.tag = pnt.tag
AND cmp.time = Date('*')
And to implement:
Code:Sub RetrieveValues()
If PIODBC_Connection Then
Dim RS As ADODB.Recordset
Set RS = New ADODB.Recordset
Set RS = Conn.Execute("SELECT cmp.Value, pnt.descriptor FROM PIcomp cmp, PIpoint pnt WHERE cmp.tag = 'SINUSOID' AND cmp.tag = pnt.tag AND cmp.time = Date('*')")
RS.MoveFirst
While Not RS.EOF
Debug.Print RS.Fields("value").Value & " : " & RS.Fields("descriptor").Value
RS.MoveNext
Wend
Set RS = Nothing
Else
End If
End Sub
Principal Consultant
Real-Time Data Management @ Wipro Technologies
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