Sql-server – Query to collect the recent TimeSampled row using inner joins in MS SQL

sql server

I have written below inner join query to get the data from my database tables. But output of this data is coming up with almost 140+ lines. Output is below. I need data in only one row with the most recent value by "TimeSampled"

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select DisplayName, ObjectName, CounterName, InstanceName, SampleValue, max(TimeSampled) as TimeSampled
from PerformanceDataAllView pdv with (NOLOCK)
inner join PerformanceCounterView pcv on pdv.performancesourceinternalid = pcv.performancesourceinternalid
inner join BaseManagedEntity bme on pcv.ManagedEntityId = bme.BaseManagedEntityId
where ObjectName = 'Processor'  AND TimeSampled >= DATEADD(MINUTE,-5,GETDATE())
AND DisplayName Like 'BLRW1ETST01.jcp.com'
AND CounterName = '% Processor Time'
GROUP BY DisplayName, ObjectName, CounterName, InstanceName, SampleValue
ORDER BY  TimeSampled desc

How I can retrive results with only last Time Sampled row with respect to DisplayName. I have multiple servers (DisplayName) like this to retrieve the data.

Thanks,
Ramu Chittiprolu

Best Answer

One way is to use the ROW_NUMBER window function to order each row grouped by DisplayName (or better, the underlying primary key, if different and DisplayName isn't indexed), then pick out the latest using the result:

SELECT DisplayName, ObjectName, CounterName, InstanceName, SampleValue, TimeSampled
FROM (
    SELECT DisplayName, ObjectName, CounterName, InstanceName, SampleValue, TimeSampled,
        OrderNum = ROW_NUMBER() OVER (
            PARTITION BY DisplayName
            ORDER BY TimeSampled DESC)
    FROM PerformanceDataAllView pdv
    INNER JOIN PerformanceCounterView pcv
    ON pdv.performancesourceinternalid = pcv.performancesourceinternalid
    INNER JOIN BaseManagedEntity bme
    ON pcv.ManagedEntityId = bme.BaseManagedEntityId
    WHERE ObjectName = 'Processor'
        AND TimeSampled >= DATEADD(MINUTE,-5,GETDATE())
        AND DisplayName LIKE 'BLRW1ETST01.jcp.com'
        AND CounterName = '% Processor Time'
) t
WHERE OrderNum = 1;

That said, there are a few oddities with your query

  • It's better to qualify column references with the table alias to avoid mishaps if same-named columns get added to different tables
  • You use LIKE for filtering on DisplayName, yet specify a simple string rather than a pattern
  • The filter on TimeSampled means, if the most recent entry for a DisplayName is more than five minutes ago, it won't be returned despite being the most recent entry, which goes against how you described the requirements
  • Be careful on thinking NOLOCK is a magic bullet (https://www.sentryone.com/blog/aaronbertrand/bad-habits-nolock-everywhere)
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