Node Availability Report (Up / Down)

Same Query from my side also 

How could I change this to filter on a specific Node Category?

Newbie question how would I use the XML you uploaded?

We have a customer that wants to know the availability of their network devices on a monthly basis. We are monitoring their network devices using an ICMP ping every two minutes. The have specified that a successful ping in the availability calculation should be given a value of 1. An unsuccessful ping should be given a value of 0. Network device availability for the month = Successful pings/Number of pings per month.  Using a two minute ping the denominator = (60/2) * 24 * days in month. 

How can i get the number of successful pings from the SolarWinds database? Would I have to pull the data hourly, or daily? Is each ping result stored separately or are they averaged?  

Is this last 30 days, or last Month's?  Your description and title conflict.

Can you explain some of the calculations?  Like some nodes show 100% availability but also show Total Down time greater than 0.  IE I have a node that shows down for 32mins, 32 secs but shows 100% availability.

This might be a good base for me, but first need to make sure it is accurate or understand how it is getting the stats.  I'm not very strong in SQL.  In the end I need a report that shows the dates a node was down and time.

Thanks