tricky sql query using CI active record

Question

I have to write this query and I think I need some help. I'm using CodeIgniter (last version) with Mysql.

I have this small table "events" with the folowing structure:

And what I want to do is to for each venue_id select 2 events.

The outcome of the query would be something like:

Venue_id number 1 : event1, event 2
venue_id number 2 : event 5, event 6

In other words, and just to be clear. I need to select 2 events per club.

I'm trying something like:

SELECT * FROM (`events`) GROUP BY `venue_id` LIMIT 2

But I need to group by and limit by venue_id

Is there a way to do this only by sql query, or should I count on php to work around it ?

Answer 1

Example, I'm a bit confused since there is no attribute active in your table, but it exists in your query.

If it's any 2 events

SELECT e1.venue_id, MIN(e2.name), MAX(e2.name) 
FROM events e1
JOIN events e2
    ON e1.venue_id = e2.venue_id
GROUP BY e1.venue_id  

Answer 2

If you just want the event id, then use group_concat() and substring_index() :

select e.venue_id, substring_index(group_concat(e.id), ',', 2)
from events e
group by e.venue_id;

If you want the full records for two venues, I'd take this approach:

select e.*
from events e join
     (select venue_id, min(id) as minid, max(id) as maxid
      from events
      group by venue_id
     ) v
     on e.venue_id = v.venue_id and
        (e.id = minid or e.id = maxid);

EDIT:

The following is one way to get up to "n" events for a given venue:

select e.*
from events e
where n >= (select count(*)
            from events e2
            where e2.venue_id = e.venue_id and
                  e2.id <= e.id
           );