Calculate median in a SQL query using different tables

Question

I have to calculate (Oracle) the median of the age of some people, but to get the ages I have to search in different tables, so the solutions provided for other questions doesn't help me.

I have 4 tables which I have to join to get the ages of the selected people and then calculate the median.

My query to get the ages is something like:

select p.year_born from patient p
where p.id in (
select distinct md.patient_id
from main_data md, treatment t, patient p, consultation c
where 1 = 1
and t.md_id = md.id 
and md.type = 'SOME_TYPE'
and c.id = p.consultation_id
and md.deleted = 0
and t.deleted = 0
and md.completed = 1
and md.patient_id = p.id
and c.testconsultation = 0);

How could I calculate the median of the years in which the people were born?

Answer 1

try this query:

WITH 
t1 as  (SELECT year_born FROM (select TO_NUMBER(p.year_born) year_born from patient p
       where p.id in (
       select distinct md.patient_id
       from main_data md, treatment t, patient p, consultation c
       where 1 = 1
       and t.md_id = md.id 
       and md.type = 'SOME_TYPE'
       and c.id = p.consultation_id
       and md.deleted = 0
       and MLP.deleted = 0
       and md.completed = 1
       and md.patient_id = p.id
       and c.testconsultation = 0)) order by year_born),
t2 as (SELECT mod(count(year_born),2) as mod_num,count(year_born) as num FROM t1),
t3 as (SELECT ROWNUM r,t1.* FROM t1),
t4 as (SELECT CASE WHEN mod_num = 1 then round(num/2) else -1 end as t4_num FROM t2)
SELECT CASE WHEN t4.t4_num = -1 then ((SELECT year_born FROM t3 where r = (t2.num/2)) +
(SELECT year_born FROM t3 where r = (t2.num/2) + 1)) / 2 ELSE (SELECT year_born FROM t3 where r = t4_num) end as final_num
FROM t4,t2;