How do I exclude outliers from an aggregate query?

Question

I\'m creating a report comparing total time and volume across units. Here a simplification of the query I\'m using at the moment:

SELECT  m.Unit,
        COUNT(         


        

Answer 1

You can exclude the top and bottom x percentiles with NTILE

SELECT m.Unit,
        COUNT(*) AS Count,
        SUM(m.TimeInMinutes) AS TotalTime
FROM    
        (SELECT
             m.Unit,
             NTILE(20) OVER (ORDER BY m.TimeInMinutes) AS Buckets
         FROM
             main_table m
         WHERE
             m.unit <> '' AND m.TimeInMinutes > 0
        ) m
WHERE   
      Buckets BETWEEN 2 AND 19
GROUP BY m.Unit
HAVING  COUNT(*) > 15

Edit: this article has several techniques too