Per the docs.Splunk entry for mstats, you can append another mstats call. So something like this should work:
| mstats count(_value) as count2 WHERE metric_name="*metric2*" AND metric_type=c AND status="success" by metric_name,env,status
| where count2=0
| append
[| mstats count(_value) as count1 WHERE metric_name="*metric1*" AND metric_type=c AND status="success" by metric_name,env,status
| where count1>0 ]
You should then be able to post-process the appended search results as desired
from User warren – Stack Overflow https://stackoverflow.com/questions/73223933/how-to-combine-count-from-two-different-mstats-in-where-clause-splunk/73226482#73226482
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