Get the rest of the row in a max group by - sql

Question

I'm trying to acquire the most recently passed training someone has taken. To do this, I have a view that works great
CREATE OR REPLACE FORCE VIEW MYAPP.most_recent_training (
employee_id, course_id, date_taken
) AS SELECT
who.employee_id,
course.course_id,
MAX(sess.end_date) date_taken
FROM employee_session_join esj
JOIN training_session sess on sess.session_id = esj.session_id
JOIN course_version vers on vers.version_id = sess.version_id
JOIN course course on course.course_id = vers.course_id
JOIN employee who on who.employee_id = esj.employee_id
WHERE esj.active_flag = 'Y'
AND sess.active_flag = 'Y'
AND course.active_flag = 'Y'
AND who.active_flag = 'Y'
AND esj.approval_status = 5 -- successfully passed
GROUP BY who.employee_id, course.course_id
Okay, so my query works excellent. Here's my problem - I also need the expiry date so I know when they go out of compliance. This is stored as a number of months on the version. But I can't add vers.valid_for_months because it complains ORA-00979: not a GROUP BY expression.
I just want to get whatever the rest of that row is. How can I do this?

Answer 1

I would think this would solve your problem:
SELECT who.employee_id, course.course_id,
MAX(add_months(sess.end_date, vers.valid_for_months))
That gets the latest end date. If you want the end date for the last session, use row_number():
SELECT employee_id, course_id, end_date
FROM (SELECT who.employee_id, course.course_id, sess.end_date,
row_number() over (partition by who.employee_id, course.course_id
order by sess.end_date
) as seqnum
FROM employee_session_join esj
JOIN training_session sess on sess.session_id = esj.session_id
JOIN course_version vers on vers.version_id = sess.version_id
JOIN course course on course.course_id = vers.course_id
JOIN employee who on who.employee_id = esj.employee_id
WHERE esj.active_flag = 'Y'
AND sess.active_flag = 'Y'
AND course.active_flag = 'Y'
AND who.active_flag = 'Y'
AND esj.approval_status = 5 -- successfully passed
) e
WHERE seqnum = 1;