Set field value as query label / alias for a PostgreSQL data source

[kovah]

Hi, I’m trying desperately to properly configure a panel using PostgreSQL as a data source. This panel has two queries from the same table with different conditions. Data is visualized via a time series.

The example output data looks like this:

date	value	meter
2023-11-12 10:11:12	0.444	Meter 1
2023-11-11 10:11:12	0.333	Meter 1
2023-11-10 10:11:12	0.222	Meter 1
2023-11-09 10:11:12	0.111	Meter 1

and similar for the second query:

date	value	meter
2023-11-12 10:11:12	3	Meter 2
2023-11-11 10:11:12	2.5	Meter 2
2023-11-10 10:11:12	2.0	Meter 2
2023-11-09 10:11:12	1.5	Meter 2

The problem: the chart shows the two graphs, but both have value as the label. Unfortunately, the PostgreSQL provides no option to set a label directly on the query.

---

• What Grafana version and what operating system are you using?

  • Grafana in Docker, v10.1.1 (0cfa76b22d)

• What are you trying to achieve?

  • I would like to set the label of a query from a field, in this case it would be the value of meter.

• How are you trying to achieve it?

  • I have no idea. I tried so many things I found on the internet, but none worked. Neither using data links in the Display Name config, nor using transforms to change the outputs. Closest I could get is with the Config from field transform, but it removes all but one query results.

---

Related but without working answer:

• Equivalent of "Alias by" with Postgres? (to customize legend text)
• Use 'query name' as 'Display name' to label series in graph
• Setting a Field label from field data after transformations - #2 by mattabrams

[yosiasz]

What kind of visualization?

Also what are the two where conditions?

[kovah]

It’s a time series, conditions select individual meters in my case.

[yosiasz]

so instead of using the column name meter, what if you tried to use

select date as time,	
       value, 
       meter as metric
  from table
 order by 1

and make sure Format is time series

bottom query is just me mocking your data

[kovah]

Thank you very much! Using metric as the name for the field worked.
May I ask how you know that it is supposed to be like that? I don’t know where in the documentation this could be found.

[yosiasz]

sorry I don’t remember where in the doc that is