I'm unable to write this query...

[Matth_S]

Hello,

I've a table on which I want to focus on 2 fields :
(id_user,id_event)

In fact, I store in this table events triggered by users while visiting a page.

So for example, my table can contain the following rows
(15,5)
(15,6)
(16,5)

etc

I want to select the id_user of users having triggered only 2 kinds of events. I want those couple of events to be 5,6 or 6,7 or 5,7 ; but I don't want to get the users having triggered the 3 events 5,6,7

First of all, I don't even know how to get the users having triggered 2 events among the list (5,6,7). The problem is, as id_event and id_user are stored in the same table, I don't know how to write the where clause to get users for whom there are 2 id_events. The only idea I've so far is to join the table with itself. But I think it will tend to be more complicated to get 2 events only among the list previously described

Thanks

[Drakla]

If you want to find out users that have two distinct events triggered then this will work

select count(DISTINCT id_event) as numevents, id_user FROM yourtable
GROUP BY id_user
HAVING numevents = 2

That doesn't add any specifics to the even numbers, but you'd use a where clause for that, such as.

select count(DISTINCT id_event) as numevents, id_user FROM yourtable
WHERE id_event IN (5,6,7)
GROUP BY id_user
HAVING numevents = 2

EDIT: the distinct will allow them to have done a single event more than one time, so if they'd done 5,5,6,5,6,6 that would still count as two distinct events, take it out if that's undesirable, or repeats never occur

[Matth_S]

Excellent ! it works perfectly.

As for the distinct, exactly what I needed, because I didn't want to take into account events triggered by the same user visting many times the same page.

Thanks for your help !