Mysql workaround for window functions

Question

I have an event table that has the following fields:

event_id
event_type 
event_time

Given a duration D and a number k<

Answer 1

Edit: Rearranged whole answer

Now I understand what you expect.

I've created such a test table on my MySQL and this seems to work:

SELECT e2.event_type FROM events e1
JOIN events e2 
    ON e1.event_time BETWEEN e2.event_time AND (e2.event_time + INTERVAL 10 MINUTE);
GROUP BY e1.event_id, e2.event_type
HAVING count(e2.event_type) >= 5

Basically, for each event you self join events with specified relative time window (from event_time to event_time + window duration), and then you group by e1's even_id to get emulated floating time window. Also we're gruping by event_type here because you want to get this field values for each window.

All you need to think through is performance. I'm not sure if it will be efficient enough for a 1M of records.