InterSystems IRIS does not have a MEDIAN SQL function. However, it has different window functions.

For example, Percent_Rank might help you here.

create table test(c1 varchar(10), c2 integer)

insert into test(c1,c2) 
select 'a',1
union all
select 'b',2
union all
select 'c',3
union all
select 'd',3
union all
select 'e',3
union all
select 'f',4
union all
select 'g',5
union all
select 'h',6

select c1, c2, Percent_Rank () OVER ( 
    ORDER BY c2 desc
) rank_no 

from test
order by c2 desc

c1  c2  rank_no
h   6   0
g   5   .1428571428571428571
f   4   .2857142857142857143
c   3   .4285714285714285714
d   3   .4285714285714285714
e   3   .4285714285714285714
b   2   .8571428571428571429
a   1   1

Doc: https://docs.intersystems.com/irislatest/csp/docbook/Doc.View.cls?KEY=RS...

Also, it's possible to create a user-defined aggregate function. See https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls...