Having trouble understanding how to nest this query

Question

I have a table
Events:
folder (Primary Key), other attributes
Reservations:
resid and folder create the primary key
I want to get attributes from the events table as well as the COUNT in the reservations table where folder=folder
So that the query returns the events attribute and the number of reservations associated with that event.
Here's what I tried ...
SELECT name, folder, start_date, end_date,
LEFT JOIN
(SELECT COUNT(*),reservations.folder FROM reservations
LEFT JOIN events WHERE events.folder=reservations.folder
GROUP BY reservations.folder)
ON reservations.folder=events.folder
FROM events WHERE events.status='Live'
ORDER BY events.folderEdited by: 928591 on Apr 21, 2012 12:31 PM

Answer 1

1. Inline View to get the reservation count per folder
2. Outer Join with events to get folder and there reservation count. Set reservation count = 0 if any event folder does not have any reservation count
3. Used oracle syntax instead of ANSI SQL to get better readability.
SELECT ev.name,
       ev.folder,
       ev.start_date,
       ev.end_date,
       NVL(res.cnt,0) reservation_count
FROM events ev,
     ( SELECT /*+ NO_MERGE */
              COUNT(*) cnt,
              folder
       FROM  reservations
       GROUP BY folder
      ) res
WHERE events.status='Live'
AND   events.folder = res.folder(+)
ORDER BY events.folder
{code}