I have the following SQL query that runs on one Orion instance.
Containers_AlertsAndReportsData.GroupName AS 'Core Network Path',
CAST(AVG(CAST(Containers_ContainerAvailability.GroupPercentAvailability as DECIMAL(10,2))) AS DECIMAL(10,2)) as 'Percent Availability'
Containers_AlertsAndReportsData with (nolock) INNER JOIN Containers_ContainerAvailability with (nolock) ON (Containers_AlertsAndReportsData.GroupID = Containers_ContainerAvailability.GroupID)
DateTime BETWEEN DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE()) - 1, 0) AND DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE()), 0) AND
Containers_AlertsAndReportsData.GroupName LIKE 'My Core Network%'
I would like to run it from the EOC and have it combine the results from 3 Orion instances.
EOC doesn't look at historical data, it primarily focuses on the current stats of Orion objects. So that data is not available for you to run your query against.
If you want to use SWQL against your Orion server, you'll need to use the Alerting entities and the Orion.ContainerStatus entity.
If you want to automate this you could script the query to run against each server .