Variable not passing to MySQL query

Grafana Data Links
1

I’ve read, and followed examples. But I’ve not been able to get a panel to acknowledge a variable sent through the URL to an MySQL query.

First, I have a bar graph with datalinks:

http://blah.org:3000/d/ab36d5d3-51a9-4615-8b82-22398e0ee912/ballerz?orgId=1&var-clantag=${__data.fields.tag}

I have tried two variable types. “Custom” and “Constant”. Currently, set to Custom:

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Clicking the tooltip on the barchart generates the URL:
http://blah.oef:3000/d/ab36d5d3-51a9-4615-8b82-22398e0ee912/ballerz?orgId=1&var-clantag=#LQQRRLC8

I can see the variable has been sent.
I have another panel with a MySQL query:
select abunchofthing where tag = ‘$clantag’;

But ‘clantag’ is never populated in the panel. it’s always blank.
What am I missing?

2

You have not provided any data to that variable that I can see

3

I’m not sure what you mean - unless you mean the definition of the variable. in which case, sure.
Is the variable supposed to contain all possible values of what I pass from the data link?

I tried what this guy did:
https://localhost:3000/t/how-to-use-url-parameters-in-mysql-queries-to-achieve-drill-down-mechanism/33179/3

If I make this variable a “constant” and supply a default value only the default value gets passed.

So, I guess I am not sure what you mean, or how the data link is supposed to tie to the variable.

1 Like
4

Yes it has to have some value otherwise it will be blank

The value can come from static stuff you type in, or from a db query or key value pair you add manually etc

I would encourage you to read the documentation first too

5

I’ve read the following documents:

It was not clear to me in any of these that a “variable” must be pre-defined in order to use it.

I made the change to make my variable a “query” type of all the possible values, but the data is still not showing up in the panel.

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The URL passed from the data link is now:
http://blah.org3000/d/ab36d5d3-51a9-4615-8b82-22398e0ee912/ballerz?orgId=1&var-clantag=#QCURQUCU

When I inspect the panel query, it still shows blank:
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I thought that would be it, and I feel closer but still not getting the desired results.
Thank you for the help.

1 Like
6

Check this out

You have it in quotes and since there is no variable named ‘$clantaf’ (with single quotes), it defaults to blank. Try removing the single quotes and see if it works.

7

That really doesn’t make any sense. The variable is encapsulated in quotes so MySQL treats it as a string. There is no variable named ‘$clantag’ as you’ve stated. If there was I would reference it was $‘$clantag’ The ‘$’ indicates it’s a variable, not the double quotes. Removing them only breaks the SQL statement further:

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The example you referenced is doing the same thing with strings:

SELECT hostname FROM my_host  WHERE hostname LIKE '$__searchFilter'

It also states:
" From Grafana 4.7.0, template variable values are only quoted when the template variable is a multi-value ."

This is not a multi-value variable, so quoting it is relevant.

I am continuing to read and try and figure out why this doesn’t work.

8

I have solved this.

First and fore most: The variable does not have to contain a pre-populated list of potential values. That is wrong information.

Second, the issue is that the data had a “#” in it, which needed to be URL encoded. I solved this by changing the datalink to this have this on the end:
&var-clantag=${__data.fields.tag:percentencode}

1 Like