Struggled with this, hope it helps someone.
In Grafana, if we base a visualization on an MS SQL query, and if we set Format as to Time series, for use in Graph panel for example, then the query must return a column named time.
This can make life difficult if we need to generate a chart, for example a Pie Chart, where we don't have a need for the time-visualization as with a bar-chart, for example.
A way around this is to return an aggregate 'time' column, like in the below:
In the above, we execute an inner query, which returns a timestamp. In the outer query we can then aggreate - 'count' - the timestamp. And the Pie Chart should work.
Took me some time and then some to figure that one out. Hope it helps!
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