Finding Nth Minimum of a Varchar value in Oracle

Question

I have an oracle table with the columns Config_ID, Escalation_Level

In this table the Escalation_Level is a Varchar with the values \'L0\',\'L1\',\'

Answer 1

If you want to find the Nth value of anything then the analytic function NTH_VALUE() is a good place to start.

Assuming you want this based on the numeric part only you have to replace everything that is not a number, for which you can use REGEXP_REPLACE()

select regexp_replace(escalation_level, '[^[:digit:]]')
  from my_table

To obtain the Nth value for a given CONFIG_ID it would be:

select nth_value(escalation_level, n)
         over ( partition by config_id 
                    order by regexp_replace(escalation_level, '[^[:digit:]]') )
  from my_table

where n is the index of the value you want to return.

Answer 2

Just a hint, you should use

RANK() OVER (PARTITION BY Config_ID ORDER BY Escalation_Level) 

in this way you will be able to make Oracle to give you the Nth position of each Escalation_Level. When you should apply a filter.

Anyway check the RANK and the DENSE_RANK analytic functions in the Oracle documentation