Window functions in SQL, unlike aggregate functions, ... Ranking functions are a type of window function that assigns a rank to each row within the partition of a result set.

Aggregate window functions are used to perform operations on sets of rows in a window(s). They include SUM() , MAX() , COUNT() , and others. Rank window functions are used to rank rows in a window(s).

To support aggregate window functions, the following two problems need to be addressed: How to make existing aggregate functions work as window function; How to handle duplicate sort key (field values ...

How to make existing aggregate functions work as window function How to handle duplicate sort key (field values in ORDER BY, will elaborate shortly) For the first problem, a wrapper class ...