Question

I have a SCORE column. How do I select the top 10% from EMPLOYEE table with top scores?

Answer 1

You could do it with analytics. Assuming that score is ascending (higher scores are better):

SELECT e.*
  FROM (SELECT e.*,
               row_number() OVER (ORDER BY score DESC)
               / COUNT(*) OVER () pct
          FROM employee e) e
 WHERE pct <= 0.1

This will select at most 10% of your employees. If there are equal scores among them, the above SQL will pick among them in a non-deterministic fashion. If you want to include all those that are in the top 10% including duplicate scores, replace row_number() by rank().

You could also use the NTILE function:

SELECT e.*
  FROM (SELECT e.*,
               ntile(10) OVER (order by score DESC) ntile#
          FROM employee e) e
 WHERE ntile# = 1