SQLTags in FSQL

Archived Topics
1

Can I read SQLTags in FSQL?

I want to add noise to a value for a demo. I have OPC tags generating random numbers. I want to multiply this random number times a value from my database. However, I don’t have and can’t buy the ODBC driver for OPC.

If I could read a SQLTag in FSQL, I could get the value from my database that way, and thought that I could do what I needed in an action item.

Alternatively, I suppose I could write a script to run periodically to do this in FPMI, but I have run up against some walls on that route.

Guidance, please. Thanks.

2

You can do this all within the SQLTags system. Make the following tags:

OPCValue = OPC Tag value from your OPC server
RandValue = DB Tag bound to a SQL Query expression doing a “SELECT RAND()”
NoiseValue = DB Tag bound to an expression that is OPCValue * RandValue

Hope this helps,

3

I would have thought that. In fact, I tried it, to no avail.

I have two SQLTags. One is reading a value from my database, the other is simulator data from KepServerEX. Both show up as good data in the SQLTags Browser.

A third SQLTag multiplies them.

{[~]Entegrity/Random/Random1A}*{[~]Entegrity/Selawik/WT1/_History/WS}

This tag contains null data and quality is “expression-eval-error”. All are floats.

4

You should get details on the expression eval error in the diagnostics page (help > diagnostics)

5

I saw the error report that you submitted about this - are you sure both tags are numeric? Maybe one is a string by mistake?

You could try throwing a toDouble() cast around both tags, let us know if that helps.

6

All were float4. When I changed the random number tags to float8, all is well. This even though the SQLTag Browser shows good data quality with either float4 or float8.