How to find matching time intervals for more than 2 users

Question

Find best suitable time from given time interval of different users.

Rows: 5
fid  userid  FromDateTime           ToDateTime          flag
62   1   2012-07-18 01:         


        

Answer 1

Using sel's schema from the fiddle (10x sel)...

The simplest way too do this is:

SELECT
    MAX(GREATEST(u1.datetime_start, u2.datetime_start)) AS MeetingStart,
    MIN(LEAST(u1.datetime_end, u2.datetime_end)) AS MeetingEnd
FROM users2 u1
INNER JOIN users2 u2
    ON (u1.datetime_end >= u2.datetime_start AND u1.datetime_start <= u2.datetime_end)
    AND u2.userid != u1.userid
    AND u2.userid IN (3,4,5)
WHERE u1.userid=2
GROUP BY u1.id
HAVING COUNT(DISTINCT u2.userid) = 3 AND MeetingStart < MeetingEnd

Change according to your situation:

In my example we have 4 participants. n=4, participants (2,3,4,5)

IN (3,4,5) --> last n-1 id's of participants to the meeting

WHERE u1.userid=2 --> id for the first participant to the meeting

HAVING COUNT(DISTINCT u2.userid) = 3 --> n - 1

Can be tested on sqlfiddle