Grafana dashboard variable - handling NULL values in Query-based variable

Question

I've created a Grafana dashboard variable (multi-select enabled) based on a MySQL query:

SELECT DISTINCT(my_field) from my_table

This field has about 12 options, one of them being a NULL value. When editing my dashboard widgets, I include a SQL constraint similar to:

... WHERE my_field IN ($my_variable)

This almost works well, except for the NULLs. Grafana is translating the NULL to '', and NULL isn't supported in an IN (...) statement anyway.

Any recommendations on how to handle this to work with NULLs?

Lukasz Szozda · Accepted Answer · 2019-08-02 20:40:28Z

4

You could extend condition:

WHERE my_field IN ($my_variable) OR my_field IS NULL;

Grafana is translating the NULL to ''

WHERE COALESCE(my_field, '') IN ($my_variable)

edited Aug 2, 2019 at 20:40

answered Aug 2, 2019 at 20:31

Lukasz Szozda

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2 Comments

radicand Over a year ago

Thanks, the trouble with this approach is that NULL isn't always selected in the dashboard as an option for the variable. I essentially need the IS NULL clause to be conditional if a null value is selected in the list of options in the dashboard drop down.

Lukasz Szozda Over a year ago

@radicand There are other options

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