SQL Query - SCOM2012R2 Performance Counter

Question

Need some assistance with a SQL query against my SCOM DW. I want this to do a select within a select. The inner select must collect the raw data for a performance counter, for the last 5 minutes. But SCOM will only give me counters that collected in the
last 5 minutes. What i want is the last value for every managed instance. - 1500 servers. 
The outer SELECT must then filter this by doing a count on how many servers it collected a value for that are above 80% - and then divide that number by the total managed servers to give me a percentage of servers above 80% memory used. Eg - it counts 10
servers are above 80%, but theres 100 servers - then gives me a final figure of 90%. 
select (count(abc.DaValue)) from (
  select
    vManagedEntity.Path
    ,vPerformanceRule.ObjectName
    ,vPerformanceRule.CounterName
    ,AVG(vPerfRaw.SampleValue) AS DaValue
  from vPerfRaw
    join vPerformanceRuleInstance on vPerformanceRuleInstance.PerformanceRuleInstanceRowid = vPerfRaw.PerformanceRuleInstanceRowid
    join vPerformanceRule on vPerformanceRule.RuleRowId = vPerformanceRuleInstance.RuleRowId
    join vManagedEntity on vManagedEntity.ManagedEntityRowid = vPerfRaw.ManagedEntityRowId
  where vPerfRaw.Datetime > DATEADD(minute, -20, GETUTCDATE())
  and vPerformanceRule.ObjectName = 'Memory'
  and vPerformanceRule.CounterName = 'PercentMemoryUsed'
  GROUP BY Path, ObjectName, CounterName, Name
  Order by DaValue DESC) 
  as abc
where abc.DaValue >= 80
This statement gives me the result
Msg 1033, Level 15, State 1, Line 15
The ORDER BY clause is invalid in views, inline functions, derived tables, subqueries, and common table expressions, unless TOP, OFFSET or FOR XML is also specified.
Any ideas ?

Answer 1

Latest update - 
SELECT count(DISTINCT abc.server) as NoOfServers,
count(case when abc.DaValue >= 90 then abc.DaValue end) 'MemoryAbove90%'
FROM( select TOP 100 PERCENT 
vManagedEntity.Path as Server ,vPerformanceRule.ObjectName 
,vPerformanceRule.CounterName ,AVG(vPerfRaw.SampleValue) AS DaValue
from Perf.vPerfRaw join vPerformanceRuleInstance on vPerformanceRuleInstance.PerformanceRuleInstanceRowid = vPerfRaw.PerformanceRuleInstanceRowid
join vPerformanceRule on vPerformanceRule.RuleRowId = vPerformanceRuleInstance.RuleRowId
join vManagedEntity on vManagedEntity.ManagedEntityRowid = vPerfRaw.ManagedEntityRowId
where vPerfRaw.Datetime > DATEADD(minute, -10, GETUTCDATE())
and vPerformanceRule.ObjectName = 'Memory' and vPerformanceRule.CounterName = 'PercentMemoryUsed'
GROUP BY Path, ObjectName, CounterName, Name
Order by DaValue DESC)  as abc
This gives me Total Servers collected from, and Total Servers found to have AVG collections over 90% for Memory Util. 
My KPI states that I must only display the number of servers that are above 90%, for more than 10minutes.
The problem with this is that when i run it over a 10 minute period, I get collections for about 40% of my managed servers only.
I want to know if anyone has a better way of collecting the perf data over a 10 minute period ? 
What i was thinking of doing is  running this query with time interval on 11 minutes, populating a temp table with the data, running the query
again with time interval on 1 minute ago, and comparing the results. IF it finds a match, I know that the server has been over 90% memory util for 10 minutes - then i can count it ? Its probably not entirely accurate, but Im out of ideas. From here, i want
to export the Values for Total Servers and TotalServersAbove90% into Excel, and build a guage off it that will reflect a % of Servers within SLA -Memory Util. 
Im not entirely familiar with SCOM collection intervals, IF I run the query for the last 1 minute - It seems to skip alot of servers and only returns
data from about 50, is that because its not cycling on those at that moment ? In which case my idea above wont work.
UPDATE 2 - i think this will do it
Our OPS guy just told me that we sample every 10min. So immediately im thinking, perhaps i can run the query for the last 11 minutes - IF more than
1 sample is above 90%, the server is above 90% for more than 10min.
But, when i run this query 
select TOP 100 Percent Path, AVG(SampleValue) AS Value, DateTime  from Perf.vPerfRaw pvpr  inner join vManagedEntity vme on pvpr.ManagedEntityRowId
= vme.ManagedEntityRowId  inner join vPerformanceRuleInstance vpri on pvpr.PerformanceRuleInstanceRowId = vpri.PerformanceRuleInstanceRowId  inner join vPerformanceRule vpr on vpr.RuleRowId = vpri.RuleRowId WHERE ObjectName = 'Memory' AND CounterName
= 'PercentMemoryUSed' AND Datetime > DATEADD(minute, -1, GETUTCDATE()) AND SampleValue >= 90 GROUP BY Path, SampleValue, DateTime ORDER BY DateTime DESC
I get a few servers, but some have more than 1 entry in the last 1 minute.  Which means that i cant compare 2 samples.
Perhaps i could say if ALL samples collected per server in that 11 minute period are > 90, 
then add 1 to MemoryAbove90%