Updated to include Availability from Orion.ResponseTime, calculated Availability (based on minutes down from Orion.NetObjectDowntime), and the number of 'Node rebooted' events from Orion.Events.
It was inspired by a question posted on the Network Performance Monitor (NPM) Forum.
There is plenty of details in the query about how the information was calculated. There's also a mention (commented out) on how to add filters for Node-based custom properties.
Important Note:
There will be a discrepancy between Availability and the Calculated Availability. This is based on the polling cycles, the pollers being used, and the way data is stored in the database. I (personally) prefer the Calculated Availability because it isn't limited to ICMP tests only.
