Question

I want to be able to perform an avg() on a column after removing the 5 highest values in it and see that the stddev is not above a certain number. This has to be done entirely as a PL/SQL query.

EDIT:
To clarify, I have a data set that contains values in a certain range and tracks latency. I want to know whether the AVG() of those values is due to a general rise in latency, or due to a few values with a very high stddev. I.e – (1, 2, 1, 3, 12311) as opposed to (122, 124, 111, 212). I also need to achieve this via an SQL query due to our monitoring software’s limitations.

Answer 1

You can use row_number to find the top 5 values, and filter them out in a where clause:

select  avg(col1)
from    (
        select  row_number() over (order by col1 desc) as rn
        ,       *
        from    YourTable
        ) as SubQueryAlias
where   rn > 5