PERCENTILE_CONT

Given an ordered set of values, this aggregate function returns the continuous percentile value, which is the value from the set that corresponds to the specified fraction. For example, percentile_cont(0.5) returns the median value. If necessary, the percentile value is interpolated in the set. See also MEDIAN() and PERCENTILE_DISC.

percentile_cont(fraction) WITHIN GROUP (ORDER BY sort_expression)

Specify a fraction between 0 and 1. The sort expression data type must be numeric.

For example:

premdb=# select max(avg_att), min(avg_att), 
percentile_cont(0.2) within group (order by avg_att) from team where avg_att>0;
  max   |  min   | percentile_cont 
--------+--------+-----------------
 75.286 | 11.189 |          24.635
(1 row)

premdb=# select max(avg_att), min(avg_att), 
percentile_cont(0.9) within group (order by avg_att) from team where avg_att>0;
  max   |  min   | percentile_cont 
--------+--------+-----------------
 75.286 | 11.189 |         54.6313
(1 row)