As opposed to the standard aggregation methods, such as Sum, Average, and Count, the new aggregation method Custom does not surround the column name or RDBMS expression with a SQL function when generating aggregated queries (e.g. SUM(<expression>), AVG(<expression>), COUNT(<expression>) . The Custom aggregation method can be used in combination with an RDBMS expression which computes an aggregated value based on a group of rows.
Read the article to learn how to use the new aggregation method in calculating percentile in Oracle.
